Dynamically resize ribbon rack

[HappyTetrahedron]

Currently the ribbon rack has a fixed width, which was chosen such that the rack fits most mobile device screens. As a result, the ribbon rack is fairly small on big screens, and a lot of space is wasted.

The ribbon rack should dynamically expand to fill that space, if available. It should only grow up to a maximum size, so it doesn't start looking weird on very wide screens.