Support new terminal protocol for extended keys and more modifiers

[maximbaz]

There is a new protocol that modern terminals will support, originally designed by fixterms and later adopted and finalized by kitty: https://sw.kovidgoyal.net/kitty/keyboard-protocol.html

Supporting this protocol will allow you to distinguish many more keys and modifiers (see the page for full list of benefits), and probably fix a bunch of open issues related to the modifiers.

[stevenxxiu]

I use Broot, and it does not detect Ctrl + M. This is probably related.

[TimonPost]

This was implemented by: #691 #696 #688