Refactor readme update script from python

[lynxplay]

The current workflow job that is responsible for updating the README.md file concerning

• [ ] page count
• [ ] reference count
• [ ] progress

uses a python3 script that exports the output into txt files.

Python3 is, at least in my opinion, overkill for this problem and can easily replaced with bash scripts. On top of that, the source count is currently calculated incorrectly, as it is only reading the amount of files in the literature folder as it should be reading the entries in the .bib file.

[tobias-schwarz]

Merge into separate Branch, do not move in next major release