Show more of the docked sidecar media panel on mobile devices

[JessicaWeinberg]

On larger screens, docked panel sidecar blocks look great. The docked panel never takes up more than 50% of the screen, always leaving room to see what's in the media panel. However, on smaller screens and mobile devices, the docked panel takes over. On a vertically oriented tablet, a the media is dwarfed by the docked panel even when there isn't a whole lot of panel content. On horizontally oriented cellphones, the docked panel takes over to the point that you can't even see enough of the media to know if you want to tap the button to expand it. See attached examples. I'd love to see more space given to the media panel in all the smaller screen docked sidecar block layouts.