I also took the freedom to add type checking, as we can't limit the
usage of `Add()` since it's a Container. The exception thrown also
advises of using the suggested `AddTrigger()` instead.
This allows for different layouts of display. Idk, maybe someone would
want to mix both variants? (don't do this please). This commit is mostly
prep for further changes.
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.
