Allow deriving ToEnum instead of just FromEnum

[FSMaxB]

I ran into a case where I had to do the conversion both ways, not just from foreign enum into my own, but also the other way round from my own enum into the foreign one.

enum_to_enum's FromEnum was a great help, because it reduces the boilerplate by half, but for the opposite direction, I still had to implement the From<MyEnum> for ForeignEnum myself.

Would it make sense to add a ToEnum derive as well?

Not sure how well this interacts with the effects though.

[abrgr]

Thanks for the issue and I'm glad enum_to_enum has been helpful!

I think deriving the opposite direction could definitely make sense. I think we could handle effects similarly to what we do now (derive From<MyEnum> for EffectContainer<ForeignEnum>).

Unfortunately, I won't be able to add this for a while. If you're interested in contributing, I am happy to guide (it should be able to work pretty similarly to the existing code). Otherwise, I will look to add this in the future.