Add vim-specific interactions to command

This mostly adds the commonly requested set (:wq and friends) and
a few that I use frequently
:<line> to go to a line number
:vsp / :sp to create a split
:cn / :cp to go to diagnostics

assets/keymaps/vim.json

@@ -18,6 +18,7 @@
           }
         }
       ],
+      ":": "command_palette::Toggle",
       "h": "vim::Left",
       "left": "vim::Left",
       "backspace": "vim::Backspace",