Fix toolbar toggling when entering/leaving fullscreen mode

[shamazmazum]

This PR fixes toolbar toggling when entering/leaving fullscreen, as the title says. This is what it looks like before the patch:

Leaving fullscreen mode:

Entering fullscreen mode:

When you press f11 (toggle-fullscreen) your toolbar does not disappear in the fullscreen mode and disappears when you leave it. When you toggle fullscreen by external means (e.g. pressing Mod+f in sway), nothing happens with the toolbar.

This patch assures that toolbar disappears in the fullscreen mode and appears in "the normal mode" in following scenarios:

• When toggle-fullscreen is invoked
• When toggling fullscreen via X11 WM /Wayland compositor
• When pressing fullscreen button on Youtube.