Description

This PR mainly adds functionality to integrate egon_data data (see issue #323).

Type of change

Please delete options that are not relevant.

[x] Breaking change (fix or feature that would cause existing functionality to not work as expected)

[x] New and adjusted code is formatted using the pre-commit hooks
~~New and adjusted code includes type hinting now~~
[x] I have commented my code, particularly in hard-to-understand areas
[ ] I have made corresponding changes to the documentation - not yet, but issue is made for it #358
[x] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes
[x] The Read the Docs documentation is compiling correctly
[x] If new packages are needed, I added them the setup.py, and if needed the rtd_requirements.txt, the eDisGo_env.yml and the eDisGo_env_dev.yml.
[x] I have added new features to the corresponding whatsnew file