Is there any easy way to get an `Iso` instance for...

# arrow

[Mitchell Skaggs]

Is there any easy way to get an Iso instance for a value (formerly inline) class? I'm just defining it manually since the @optics annotation doesn't support it. It might be useful for composition and seems relatively easy to add to the @optics annotation if it's not supported elsewhere.

(This might be better suited for #arrow-meta since it deals with the optics plugin, idk)