Adapt to "Keep a Changelog" (#3634)

- Adapt heading and description to "Keep a Changelog" guideline v1.1.0
- Add missing links at the end - with this, users can click on the
version number to see the diffs (I think this was intended from the
beginning)
- Fix two bare URLs

## The link fix
Before (the link on the version number doesn't work):
![Screenshot from 2024-11-14
01-15-07](https://github.com/user-attachments/assets/e0ff4eee-abc8-4ba8-9fb7-f18fd3279ddf)

After (the link on the version number works):
![Screenshot from 2024-11-14
01-15-52](https://github.com/user-attachments/assets/7b2997e7-cf6d-4e23-b4fc-50536174f4c6)

Collaboration.md

@@ -33,6 +33,7 @@ Are done by
 - [ ] update `CHANGELOG.md`
   - [ ] add all contributor names: `...`
   - [ ] add min. node version: > ⚠️ This release needs nodejs version `v20` or `v22`, minimum version is `v20.9.0`
+  - [ ] check release link at the bottom of the file
 - [ ] commit and push all changes
 - [ ] after successful test run via github actions: create pull request from `develop` to `master` branch
   - [ ] add label `mastermerge`
@@ -49,6 +50,7 @@ Are done by
 - [ ] checkout `develop` branch
 - [ ] update `package.json` and `package-lock.json` to reflect correct version number `2.xx.0-develop`
 - [ ] draft new section in `CHANGELOG.md`
+  - [ ] create new release link at the bottom of the file
 - [ ] commit and publish `develop` branch
 
 ### After release