Extra completion-at-point function extensions for usability

[jeff-phil]

• Added :company-doc-buffer function, to show full completion text which includes markdown where available to pretty up the doc
• Added :company-kind to show "magic" icon indicator.
• Added :company-annotation in order to show capf source in disp
• Made a few small edits to :exit-function that did not appear to have correct lexical binds.

Here is result on my machine using corfu/cape as the capf front-end.

Item #8 in the list is high-lighted, and to the right the help document displays showing the full completion text in markdown using buffer language (python here) for the font-lock. If markdown is not installed, plain text will be shown but still with line breaks vs. how displays in listing on one-line.

There is also a magic wand icon to the left of Codeium completion, that gives indicator it is from Codeium completion. And (if the completion text wasn't so long in this example) would also show Codeium on the left for the annotation.

[fortenforge]

Cool! please fix the typo

[jeff-phil]

Oops. Typo fixed. Thanks!