Add 'CFunctorWithIndex', 'CFoldableWithIndex', and 'CTraversableWithIndex' typeclasses?

[noinia]

It would be nice to have these typeclasses, mirroring the ones from https://hackage.haskell.org/package/indexed-traversable would you be open to adding those?

[konn]

Ah, it is definitely good to have constrained counterparts of those! I don't have any particular schedule to work on this for the moment, but could be added when I've got enough time to work on it. If you have any implementation plan, PRs are always welcome!