Prepare release v0.8.0

[martin4861]

Summary

Prepare CHANGELOG.md for the next release as per #314.

Checklist:

• It is my own work, its copyright is implicitly assigned to the project and no substantial part of it has been copied from other sources (including Stack Overflow). In rare occasions this is acceptable, like in CMake modules where the original copyright information should be kept.
• I'm using the same code standards as the existing code (indentation, spacing, variable naming, ...).
• I've added tests for my code.
• I have verified whether my change requires changes to the documentation
• My change either requires no documentation change or I've updated the documentation accordingly.
• My branch has been rebased to main, keeping only relevant commits.

[martin4861]

@ursfassler @shirzartenwer Would you be able to review and merge this PR and then create a v0.8.0 on main? Thanks a lot in advance!

[ursfassler]

Thank you very much. Looks good overall, just 2 small adjustments needed.

[ursfassler]

Thank you, looks good