Add doi, improve doc

[jlaehne]

Add zenodo doi to documentation and improve landing page

Progress of the PR

• [x] Change implemented (can be split into several points),
• [x] ready for review.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.27%. Comparing base (86cabf2) to head (a4c2ee9).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #27 +/- ## ======================================= Coverage 87.27% 87.27% ======================================= Files 7 7 Lines 330 330 Branches 73 73 ======================================= Hits 288 288 Misses 25 25 Partials 17 17 ```

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