feat: Disallow untyped decorators

See
<https://mypy.readthedocs.io/en/latest/command_line.html#cmdoption-mypy-disallow-untyped-decorators>.

Author: l0b0

mypy.ini

@@ -3,6 +3,7 @@ disallow_any_generics = True
 disallow_incomplete_defs = True
 disallow_subclassing_any = True
 disallow_untyped_calls = True
+disallow_untyped_decorators = True
 disallow_untyped_defs = True
 ignore_missing_imports = True
 no_implicit_optional = True