Add types.ModuleType.__doc__ (#12918)

Author: AlexWaygood

stdlib/types.pyi

@@ -337,6 +337,13 @@ class ModuleType:
     __package__: str | None
     __path__: MutableSequence[str]
     __spec__: ModuleSpec | None
+    # N.B. Although this is the same type as `builtins.object.__doc__`,
+    # it is deliberately redeclared here. Most symbols declared in the namespace
+    # of `types.ModuleType` are available as "implicit globals" within a module's
+    # namespace, but this is not true for symbols declared in the namespace of `builtins.object`.
+    # Redeclaring `__doc__` here helps some type checkers understand that `__doc__` is available
+    # as an implicit global in all modules, similar to `__name__`, `__file__`, `__spec__`, etc.
+    __doc__: str | None
     def __init__(self, name: str, doc: str | None = ...) -> None: ...
     # __getattr__ doesn't exist at runtime,
     # but having it here in typeshed makes dynamic imports