Feat vim mode

[rileyhawk1417]

This PR is meant to support Vim Mode in the main AppFlowy app. It does not conflict with the main editor and can be toggled on/off easily.

The documentation for it is a WIP and can be found at here.

Checklist:

• [x] Support basic keys [h, j, k, l]
  • [x] Test Written
• [x] Support line jumping (e.g 4j, 10l)
  • [x] Test Written
• [x] Undo & Redo
  • [x] Test Written
• [x] Exit to Normal Mode and Insert Mode
  • [x] Test Written
• [ ] Text selection