separate typetest-analyse into multiple modules

[MasterMedo]

Separating the typetest-analyse logic to multiple files.

Please complete these tasks before opening your PR:

• [x] separate plot functions into individual files
• [x] rename variables to more sensible names
• [x] improve logic in typing_speed_per_test
• [x] improve logic in typing_speed_per_test_duration
• [x] take out generating least_typed_words and worst_words from typetest-analyse
• [x] plot all charts by default
• [x] add file not empty checks in check_files
• [x] rename check_files to check_input_file_path
• [x] My PR has been formatted with black, i.e. poetry run black .
• [x] My PR passes the tests, i.e. poetry run python -m unittest

[MasterMedo]

I don't expect you do a full quality review.

This is more of a sanity check, you can clone, try a few things out and if it works, we ship it. I don't have to publish to PyPI since no new functionality was introduced. We'll fix the bugs as we encounter them. 💪