fix byte-compiler, checkdoc, package-lint warnings

[conao3]

Hi!, I found this package, I fixes some warnings. I file this PR as a first my contribution step!

before

 fzf.el     0     info            You should have a section marked ";;; Commentary:" (emacs-lisp-checkdoc)
 fzf.el     1   1 error           Package should have a ;;; Commentary section. (emacs-lisp-package)
 fzf.el     1   1 warning         The package summary should not end with a period. (emacs-lisp-package)
 fzf.el    11   4 warning         You should include standard keywords: see the variable `finder-known-keywords'. (emacs-lisp-package)
 fzf.el    54   1 error           `fzf/window-height' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    55     info            First sentence should end with punctuation (emacs-lisp-checkdoc)
 fzf.el    59   1 error           `fzf/executable' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    64   1 error           `fzf/args' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    69   1 error           `fzf/git-grep-args' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    70     info            First sentence should end with punctuation (emacs-lisp-checkdoc)
 fzf.el    70     info            There should be two spaces after a period (emacs-lisp-checkdoc)
 fzf.el    74   1 error           `fzf/position-bottom' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    75     info            There should be two spaces after a period (emacs-lisp-checkdoc)
 fzf.el    79   1 error           `fzf/directory-start' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    84   1 error           `fzf/window-register' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    85     info            First line is not a complete sentence (emacs-lisp-checkdoc)
 fzf.el    86     info            There should be two spaces after a period (emacs-lisp-checkdoc)
 fzf.el    90   1 error           `fzf/grep-cmd' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    91     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el    97   1 error           `fzf/after-term-handle-exit' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    98     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   114   1 error           `fzf/start' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el   115     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   137  44 warning         assignment to free variable ‘term-suppress-hard-newline’ (emacs-lisp)
 fzf.el   145   1 error           `fzf/vcs' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el   146     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   151   1 error           `fzf/git-files' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el   152     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   159     info            Probably "Starts" should be imperative "Start" (emacs-lisp-checkdoc)
 fzf.el   167     info            Probably "Starts" should be imperative "Start" (emacs-lisp-checkdoc)
 fzf.el   173     info            Probably "Starts" should be imperative "Start" (emacs-lisp-checkdoc)
 fzf.el   179     info            Probably "Starts" should be imperative "Start" (emacs-lisp-checkdoc)
 fzf.el   185     info            Probably "Starts" should be imperative "Start" (emacs-lisp-checkdoc)
 fzf.el   191     info            Probably "Starts" should be imperative "Start" (emacs-lisp-checkdoc)
 fzf.el   198     info            Second line should not have indentation (emacs-lisp-checkdoc)
 fzf.el   198     info            First line is not a complete sentence (emacs-lisp-checkdoc)
 fzf.el   198     info            Probably "Starts" should be imperative "Start" (emacs-lisp-checkdoc)
 fzf.el   198     info            There should be two spaces after a period (emacs-lisp-checkdoc)
 fzf.el   206   1 warning         the following functions are not known to be defined: turn-off-evil-mode, term-char-mode, projectile-project-root (emacs-lisp)

after

 fzf.el    58   1 error           `fzf/window-height' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    63   1 error           `fzf/executable' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    68   1 error           `fzf/args' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    73   1 error           `fzf/git-grep-args' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    78   1 error           `fzf/position-bottom' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    83   1 error           `fzf/directory-start' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    88   1 error           `fzf/window-register' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    93   1 error           `fzf/grep-cmd' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el    94     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   100   1 error           `fzf/after-term-handle-exit' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el   101     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   117   1 error           `fzf/start' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el   118     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   139  44 warning         ‘term-suppress-hard-newline’ is an obsolete variable (as of 27.1). (emacs-lisp)
 fzf.el   147   1 error           `fzf/vcs' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el   148     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)
 fzf.el   153   1 error           `fzf/git-files' contains a non-standard separator `/', use hyphens instead (see Elisp Coding Conventions). (emacs-lisp-package)
 fzf.el   154     info            All variables and subroutines might as well have a documentation string (emacs-lisp-checkdoc)

Note

term-suppress-hard-newline is marked as a obsolete variable from Emacs-27.`

[bling]

thanks for the contribution, @conao3. can you please rebase against the latest? there was a major enhancement in the other PR that i wanted to get merged first.