small improvements to PyPI explanation

[LisaSikkema]

Added some missing information that would have made the PyPI instructions clearer for me, feel free to adapt if necessary

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.02%. Comparing base (d3e595d) to head (753ab61).
⚠️ Report is 45 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #207       +/-   ##
===========================================
- Coverage   63.33%   51.02%   -12.32%     
===========================================
  Files           7        7               
  Lines          30       49       +19     
===========================================
+ Hits           19       25        +6     
- Misses         11       24       +13     

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[flying-sheep]

@LisaSikkema this should go into https://github.com/scverse/cookiecutter-scverse, not here.

Also please don't use inline links. Looks like @Zethson accidentally broke the PyPI links in scverse/cookiecutter-scverse#369. The fix should be to restore the link targets: scverse/cookiecutter-scverse#369 (comment)