So this is the first commit where we are starting to migrate from tmux.
Right now I'm not sure how this will go, every other attempt has not
lasted very long.
This does support all the features I am using in tmux though. TBH most
of the stuff in the tmux.conf wezterm does by default. For example, the
pain numbers start at 1 not 0.
This implements a fork of tmux navigation, the plugin I have been using
in vim since like.... day one.
Ade Attwood
6b939f0486