Allow implementing From and TryInto

[charles-r-earp]

I might even submit a PR for this. It's a common pattern when using enums to implement MyEnum From<Variant> for each variant, and likewise it would even be nice to have the reverse, TryInto<Variant> for MyEnum.
Notably the enumerate crate does implement From, but it isn't as flexible, it can't be combined with attributes like derive.

[NyxCode]

Totally agree, From & TryInto implementations would be awesome. I'd appreciate a PR!