Add typehints

[twsl]

In order to understand the current issues with the passed data, I tried to add type hints to the library

[timvink]

Thanks for this! Some nice house keeping :)

Couple of small remarks.

And yes I should have run a code formatter like ruff on top of this plugin, and set it up as a pre-commit hook.

[twsl]

@timvink let's handle ruff in a separate PR, everything else should be good to go