`:exit` should be `:exi[t]` instead of `:ex[it]`, `:ex` has different
command

- https://neovim.io/doc/user/editing.html#%3Aex
- https://neovim.io/doc/user/editing.html#%3Aexit

Changes:
- Add `:ex` same as `:edit`
- Change `:ex[it]` to `:exi[t]`

Release Notes:

- N/A