Some changes to the header (square logo on small, menu button is
colored differently, header is taller), making it so the page doesn’t
scroll to the top when the sidebar is opened on small, adding an
overlay over the page when the sidebar is opened on small. Also, the
square logo needs to be defined in LocalSettings.php as mobileimg (I
made a temporary logo called brickismall.svg). I’m going to make some
more changes later; please feel free to give feedback on what’s here so
far though.