Hide servers and channels panels

Add options for hiding servers and channels panels by clicking a button and showing when hovering over them with cursor to let the user concentrate on what it cares instead of always having both persistently in sight. In the meantime, who uses the official app can't hide them, who uses a snap, flat or any other package can if its developers added them since they are sandboxed and who uses the browser version can by installing the extension Hide Discord Sidebar.