Since the numeric layout got supported, the XML file defining the layout
was required. Add it to the list of required layouts in the README so
users can still install and run the current keyboard.
Fixes: e5d0716c0f ("core: button: add support for layout switching keys")
Link: https://gitlab.com/flamingradian/unfettered-keyboard/-/issues/7
Having multiple input methods at once causes behaviour defined by the
Wayland compositor. In a recent update by Phoc, the most recently
started input method would take priority to demonstrate the instability.
Add a configuration option so the Wayland input method can be disabled
to accommodate a second input method.
Also update the README with the new option.
