Add changelog

[peanutfun]

Changes proposed in this PR:

• Add a CHANGELOG.md file to keep track of changes
• Update PR description template and Git development guide accordingly

I think keeping a changelog makes much more sense than having the Upcoming Release overview that is detached from the code base.

PR Author Checklist

• Read the Contribution Guide
• Correct target branch selected ❗ main
• Source branch up-to-date with target branch
• Documentation updated
• [ ] Tests updated
• Tests passing
• No new linter issues

PR Reviewer Checklist

• Read the Contribution Guide
• CLIMADA Reviewer Checklist passed
• Tests passing
• No new linter issues

[emanuel-schmid]

Good idea! 👍
Just one question - why don't we merge it into develop first?

[peanutfun]

why don't we merge it into develop first?

Because the PR templates on GitHub are always taken from main. If we merge into develop, I fear that nobody will notice we have a changelog, as there will be no new item in the Checklist until we merge develop into main 🤓

My proposal would be to merge this into main, then merge main into develop in a new PR.

[emanuel-schmid]

I see, yes, makes sense. Let's try 😁