fix UnionType.__or__ and add UnionType.__getitem__

Author: KotlinIsland

stdlib/types.pyi

@@ -717,10 +717,13 @@ if sys.version_info >= (3, 10):
         def __args__(self) -> tuple[Any, ...]: ...
         @property
         def __parameters__(self) -> tuple[Any, ...]: ...
-        def __or__(self, value: Any, /) -> UnionType: ...
-        def __ror__(self, value: Any, /) -> UnionType: ...
+        # the `Any` is because of underspecified binop semantics, when the rhs is a `_SpecialForm`
+        #  it might result in a `_SpecialForm` (Union)
+        def __or__(self, value: Any, /) -> UnionType | type | Any: ...
+        def __ror__(self, value: Any, /) -> UnionType | type | Any: ...
         def __eq__(self, value: object, /) -> bool: ...
         def __hash__(self) -> int: ...
+        def __getitem__(self, parameters: Any) -> object: ...
 
 if sys.version_info >= (3, 13):
     @final