Support for alternative keyboard protocol

[deathaxe]

This issue affects applications interacting with FISH Shell 4.0+, which sends \x1b[=0u and \x1b[=5u sequences by default.

related with: https://github.com/fish-shell/fish-shell/issues/11054

implementation details: https://sw.kovidgoyal.net/kitty/keyboard-protocol/

It causes Terminus package for Sublime Text to display misterious 0u and 5u characters in terminal output.

see: https://forum.sublimetext.com/t/latest-dev-builds-broke-terminus-with-fish-shell/75587/6

Originally posted by @deathaxe in #141