Wayland region selection

Uses gtk-layer-shell therefore a compositor that supports wlr-layer-shell-unstable-v1 is required.

To align expectations, the target compositor is labwc, working correctly when using other compositors is a nice to have.

Known glitches

• Start dragging from one of the monitors make the size window darker on the other.
• Wayfire: Size window disappears when the cursor moves to another monitor.
• Sway: Size window always shown on first monitor.
• Wayfire: rectangle size text shown in the screenshot
• Sway & Wayfire: if cursor is moved slowly to another monitor, there will be rendered artifacts left on the previous monitor
• Labwc: mouse button click while dragging prevents selection rectangle from rendering on the other monitor when cursor moves to it
  • I was unable to fix this, however, clicking any button again corrects the selection area, it's nothing serious just annoying