feat(Underglow): Momentary effect selection

[ReFil]

Adds the ability to have an RGB effect select whilst held down and revert when released.

Designed to be used in conjunction with #1456 to allow for momentary battery indication through the lighting by holding down a specific key

[ReFil]

I've edited the documentation to note the new command as well as notes around an edge case when it's powered off with the key held down. Thinking about this I've realised the functionality can now be done using a parameterised macro too, however i think a dedicated behaviour command still has value. A parameterised macro would also present the same issue on the edge case when it's powered off with the key held down, I cant think of a good way to mitigate this (If anyone has ideas i'm happy to implement them)

[caksoylar]

I think the macro approach would hit #1494 as well, and I assume this works without issues for splits.

[ReFil]

I'll double check, a variant of this has been in use on the 360 Pro but the 360 pro doesn't use the standard locality implementation

[caksoylar]

LGTM, small nit on the formatting in the table.

[ReFil]

Studio metadata has now been added. I think I've done it right but would appreciate someone more knowledgeable on the metadata looking over it