fix: make maximize workaround windows specific

[christoph-heinrich]

ref. #203 (comment)

[christoph-heinrich]

Turns out there is a race condition here on wayland. Happens on both kwin and weston.
The compositor ignores the unmaximize request if mpv is still considered fullscreen. For me it depends on the CPU usage if the timing works out or not.

I guess the simplest way to deal with that would be to add a small delay between setting fullscreen and setting window-maximized and hope it's enough, or a hook that waits for fullscreen to change before setting window-maximized.

No idea if other platforms might have the same problem.

Edit: hook doesn't work reliably. Delay of 0.1s works but is noticeable and 0.01s works unreliably. 0.02s looks to be reliable for me, but I'm not a big fan of fixed time delays...

Alternatively the button could always only unfullscreen and not touch maximized if fullscreened.