Feature request: inline comment support

[sersorrel]

debug info

```json { "atom": "1.45.0", "platform": "linux", "release": "4.15.0-91-generic", "vmpVersion": "1.36.4", "vmpConfig": { "charactersToAddSpaceOnSurround": [ "(", "{", "[", "<" ], "stayOnVerticalMotion": false, "useSmartcaseForSearch": true } } ```

Checklist

You have to check all before open issue.

• [x] Provide your environment info clipped by Vim Mode Plus: Clip Debug Info command.
• [x] Try with latest Atom and latest vim-mode-plus.
• [x] Pick a descriptive and non-ambiguous subject
• [x] Express "what" you want(feature? config option?, behavior change?) in short sentence(not long!).
• [x] Contrast current behavior if you want to change current behavior, with sample text, operation(keystroke) and result.
• [x] Include real use case so that maintainer can understand "why" you need help.
• [x] Include Atom(atom --version), vim-mode-plus version, and OS version(e.g. macOS Sierra 10.12.3).

  • $ atom --version
    Atom    : 1.45.0
    Electron: 4.2.7
    Chrome  : 69.0.3497.128
    Node    : 10.11.0

  • vim-mode-plus 1.36.4
  • Ubuntu 18.04
• [x] If keybinding issue, Read this.

I set up a mapping similar to vim-commentary:

"atom-text-editor.vim-mode-plus:not(.insert-mode)":
  "g c": "vim-mode-plus:toggle-line-comments"

however, this doesn't work well (obviously) for if you have part of a line selected and you want to insert a block comment without commenting out the rest of the line.

tcomment supports inline comments, where only part of the line is commented out – could vim-mode-plus also support this?

i.e. having some visual-mode selection of less than a full line and pressing gc would use a block comment to comment just the selection out, rather than a line comment.