Vi mode (READ: Allow selection keys to be rebound to different keys)

# Description of the new feature/enhancement

This issue suggests implementing a "Vi mode" similar to the very convenient one implemented by Alacritty, where the user can
move the cursor around, select and copy text using the keyboard alone in a fashion familiar to most programmers and power users;

* The user presses a predefined keyboard shortcut to enter Vi mode
* Once in Vi mode, the cursor is movable in the current terminal buffer using Vi motions (h j k l)
* 'V' enters visual mode, where text can be selected and copied ('y')
* '/' and '?' enter search mode where text can be searched and then copied

Start by reviewing the issue requirements and the Vi mode implementation in Alacritty, focusing on the requested shortcut, h/j/k/l motions, visual selection, copying, and / and ? search behavior. Done means users can enter Vi mode, navigate the current terminal buffer, select and copy text, and search using the keyboard alone.

Written by the indexing model from the issue text.