Create a challenge for PEP 646: variadic generics and `TypeVarTuple`

[laike9m]

PEP 646

[F-park]

I find a new challenge about type-variable-tuple-equality, should we add this?

[laike9m]

There are always edge cases for which more challenges can be added. This usage seems uncommon, but I see no reason why we can't have one challenge for it.