Fix broken TypedDict compatibility with older versions of python

By missing to declare the Model as a generic dictionary type we cause
the script to fail because the TypedDict is not supported by older
versions of python (e.g. 3.6, 3.7).

jc/parsers/xrandr.py

@@ -297,6 +297,7 @@ except ImportError:
     Device = Dict[str, Union[str, int, bool]]
     Frequency = Dict[str, Union[float, bool]]
     Mode = Dict[str, Union[int, bool, List[Frequency]]]
+    Model = Dict[str, str]
     Response = Dict[str, Union[Device, Mode, Screen]]