Insert Mode
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The key bindings in this mode is the same as in the emacs mode
except for the following 4 keys. So, you can move around in the buffer
and change its content while you are in insert mode.
`<ESC>'
This key will take you back to vi mode.
`C-h'
Delete previous character.
`C-w'
Delete previous word.
`C-z'
Typing this key has the same effect as typing <ESC> in emacs mode.
Thus typing `C-z x' in insert mode will have the same effect as
typing `ESC x' in emacs mode.