A StructVariant DynamicEnum always returns None from the field_at method

[jhgarner]

Bevy version

0.16

What you did

I tried to use the field_at method on a StructVariant DynamicEnum.

What went wrong

The docs for field order say that field_at should be implemented for struct variant enums. Since DynamicEnum is builtin, I expect it to follow that convention, but the DynamicEnum implementation doesn't follow it. Is it possible for DynamicEnum to follow this convention? If it isn't, could this be called out in the docs?

[alice-i-cecile]

Just looks like an oversight. We'd appreciate a PR to fix this!