Release instructions in readme.adoc don't work as described

[martinmo]

At the moment, the release instructions in the readme don't work as described.

• Running the ChangelogCreator requires an undocumented env.properties file with GitHub credentials. The tool was written when the repo was private. In the meantime, because the operations are read-only, I think the authentication can be left out entirely.
• ChangelogCreator fails for milestones with only one closed issue (com.jayway.jsonpath.PathNotFoundException: No results for path: $[1]['milestone']['title']).
• It should be noted that the preparation commit which creates the changelog entry and updates information about the latest release in index.adoc must be committed to the maintainance branch and cherry-picked to main.
• Running mvn release:prepare on branch 7.3.x didn't work (Can't release project due to non released dependencies : [ERROR] org.moduliths:moduliths-test:jar:1.1.0-SNAPSHOT:test). Seems like the version for that dependency is missing only in the 7.3.x branch. I will create a separate issue for that (#349).
• Before mvn site:deploy -Pdocs, the there should be an invocation of mvn package -Pdocs -Prelease or something similar, otherwise the AsciiDoc files won't be processed.

[martinmo]

I have added the information that I've gathered through trial and error today to the release instructions. I am not 100% satisfied with the process (it now seems a bit complex), but it works.