All other similar UI components have required dependencies, so this is
mainly to bring things in line with expectations. I am using this fact
in the skin editor to only show components which can be used in the
current editor context (by `try-catch`ing their
`Activator.CreateInstance`).
This is kind of how I see things working going forward, where the editor
can be applied to anything in the game which supports it (ie. a results
screen, gameplay screen, etc.) and it will immediately allow changing
the interface.
This adds a test scene which shows this working with gameplay.
