Readme cleanup

[firai]

• Key binding lists
  • [x] Fix the "Esc, Ctrl-[" key binding, which would have meant pressing these in succession, to say "Esc or Ctrl-[".
  • [x] Reword the descriptions of "Shift-Esc" and "Esc or Ctrl-[" to be more accurate.
  • [x] Reword the descriptions for changing cell type to be similar to those in JupyterLab.
  • [x] Consistency in abbreviations and capitalization
  • [x] Esc
  • [x] Cmd
  • [x] Reorder vim bindings and Jupyter command bindings to put the corresponding bindings in the same order.
• Elsewhere
  • [x] Fix grammar in various places.
  • [x] Flip order of Normal and Insert modes in the mode list, based on the order that they are entered relative to Command mode, i.e., how they would be ordered in a flow diagram.
  • [x] Change the key binding explanation to use <kbd> tags based on semantics. (However, to retain consistency with the style in vim help files, the key bindings in the lists still use hyphens between the keys.)
  • [x] Uniformly make mode names capitalized and "mode" itself lowercase in paragraph text. (Key binding descriptions have been left as title case only to minimize change. I wouldn't be opposed to making these sentence case.)

[github-actions[bot]]

:point_left: Launch a Binder on branch firai/jupyterlab-vim/readme-cleanup