feat(types): Add type hints and code optimizations

[benatouba]

DISCLAIMER: I know this is a lot of changes and might be rejected or a lot of changes requested. But I like to work with typed functions much better and think someone might also benefit from this. This will definitely require additional changes in the future, but I feel it could be a start. All tests passed locally (no google API key).

Python3.8 is almost end-of-life and backwards compatibility to versions before type hints is not a priority any more.

This commit is a start and by no means complete or correct for all instances.

Furthermore, I included code optimizations. These mainly regard raising of exceptions, pytest style tests and some minor refactoring.

• [x] tests added / passed
• [ ] passes git diff upstream/master | flake8 --diff This is not true for some lines, but most of these would not pass a default flake8 config without the changes. Formating is done via ruff formatter in black style.
• [x] Introduces Type annotations/type hinting for easier use of the library

[fmaussion]

Thanks! I'm away on leave starting tomorrow so I wont have a look until later in the summer, but a few things already:

• this is too much for one commit - it needs to be split into separate commits

• I'm okay with black, but this has to be done in a separate commit only and this needs to be removed from blame. We also need to enforce this in CI then

• I'm also okay with type hints although I always thought its overkill for a library like salem

• but somehow there are still some salem users around. Maybe I should do a survey one day.

[benatouba]

Ok. I will split this up into multiple, well organized commits. However, this will only happen in a couple of weeks.

• I actually do not really like black's formatting style, but was unsure of the style guide used in the project.
• Thank you for the tip to remove from blame. I did not know that this was possible.