Update `prer` to use commit messages and or PR content so release notes can be generated

### Description of the problem / feature request:
Previously we were able to construct release notes by hovering over the commit hashes but GitHub has removed showing previews of the PRs linked to the commits.

The commit history on the PR branch can no longer be used to crate release notes easily

### Feature requests: what underlying problem are you trying to solve with this feature?
prer should automate or make it easy to view all the commit messages that resulted in the manifest changes. E.g. automate the release notes.

### Have you found anything relevant by searching the web?

Automating release notes via commit messages: https://www.conventionalcommits.org/en/v1.0.0/

Das Issue nennt `prer`, aber keine Dateien oder Tests. Beginne damit, den Code zu finden, der Manifeständerungen und die Release-Ausgabe verarbeitet, und ermittle dann, wie Commit-Nachrichten oder Pull-Request-Inhalte verfügbar sind; fertig ist die Aufgabe, wenn `prer` Release Notes für die Commits hinter Manifeständerungen anzeigen oder erzeugen kann.

Vom Indexierungsmodell aus dem Issue-Text verfasst.