keybindingHandler: maximize vertically/horizontally without gaps

[Leleat]

When maximizing a window vertically or horizontally, we've added gaps to the window like we normally do to tiled windows. This makes sense if the window is already tiled. If the window is floating, we shouldn't add gaps to it and instead should keep the currently visible size.

Fixes https://github.com/Leleat/Tiling-Assistant/issues/349

[F-i-f]

Confirming that this patch fixes #349.