Allow Greedy[X] | Y

Constructs a Union. Needs to be special instance behavior due to
`__class_getitem__` being implemented to return an instance not a type
or GenericAlias.

discord/ext/commands/converter.py

@@ -1140,6 +1140,9 @@ class Greedy(List[T]):
         converter = getattr(self.converter, '__name__', repr(self.converter))
         return f'Greedy[{converter}]'
 
+    def __or__(self, value: Any) -> Any:
+        return Union[self, value]
+
     def __class_getitem__(cls, params: Union[Tuple[T], T]) -> Greedy[T]:
         if not isinstance(params, tuple):
             params = (params,)