x11/shotman: add new port

The uncompromising screenshot GUI for Wayland compositors.

shotman takes a screenshot and shows it in a small floating thumbnail window.
The screenshot can then copied with Ctrl+C, deleted with D, or dismissed
with Esc.

shotman is designed to run in response to some global hotkey (e.g.: Super+P,
PrintScreen, etc). It is designed for interactive usage.

https://git.sr.ht/~whynothugo/shotman
(cherry picked from commit 837378593f788395368ec343c79abcb07cc3a12d)