Add type hints to description.py

[KoStehner]

Hello,

I added annotations to tables/description.py.

The annotations were a bit tricky sometimes since we handling with class objects instead of instances of classes here.
For this, the typing.Type hint was used. See also

• https://docs.python.org/3.9/library/typing.html#typing.Type

Best regards
Ko

[avalentino]

Thanks @KoStehner