pretty sure sadd should take a KeyT not an str for the key name

This function:

```
    def sadd(self, name: str, *values: FieldT) -> Union[Awaitable[int], int]:
```

differs from all other key functons in that the name is a "str", however there is no documentation that says it must be an str.  all keys are "bytes safe" from the docs.   should probably change all the set functions to KeyT.   

Unless anyone disagrees, happy to put up a PR.