The mouse position is saved and restored when focusing another screen
If the target screen has no saved mouse position, the relative position
of the current screen is used
Signed-off-by: lesell_b <lesell_b@epitech.eu>
This still does `client.focus = c` by default, but allows to customize
it.
This was initially suggested in #194, but by using `request::activate`
instead, which would not be the same. Therefore a new signal is being
used instead.
Helped-by: Samir Benmendil <samir.benmendil@gmail.com>