Add the ability for wayland output to grab input

This change, adds the option to create a keyboard shortcut, that when pressed confine the pointer to the currently focused wayland output and inhibit keyboard shortcut (if the system compositor supports these features, e.g. sway, kwin, mutter).

Pressing the shortcut again, will release the pointer and keyboard.

the shortcut can be set either by compositor with the function "wlr_wl_backend_set_grab_input_shortcut" (by specifying modifiers as mask and a key symbol)

or by the user with the environment variable WLR_WL_GRAB_INPUT_SHORTCUT (list of modifiers and a key, sperated by "+", e.g. shift+alt, control_r, shift+mod4+o).