[WIP] Xresources shortcuts

[neeasade]

Keybinds are being registered, the command is not associated yet.

Edit: The goal for this is to be able to for example in your xresources:

st.kb_alt_l: notify-send "you pressed alt L!"

or callout to some script that we may give context through env variables (rn just using externalpipe function to give child the terminal contents)

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fixes #29

[actionless]

nice idea, good luck with finishing it up

[RaafatTurki]

this would be an awesome feature to have, I'm assuming this also allows the ability to override builtin shortcuts.

you should make a checklist of micro-tasks so others (like me) can send in PRs regarding this.