x11/wl-mirror: add new port

wl-mirror attempts to provide a solution to sway's lack of output
mirroring by mirroring an output onto a client surface.

Features:

• Mirror an output onto a resizable window
• Mirror an output onto another output by fullscreening the window
• Reacts to changes in output scale
• Preserves aspect ratio
• Corrects for flipped or rotated outputs
• Supports custom flips or rotations
• Supports mirroring custom regions of outputs
• Supports receiving additional options on stdin for changing the mirrored screen or region on the fly (works best when used with pipectl)

https://github.com/Ferdi265/wl-mirror
(cherry picked from commit 4ae14ebeac238aef26fa234429f14eec5a5cb03d)