[Merged by Bors] - Adds a note to the readme that this project has been retired

[soenkeliebau]

Description

In preparation for archiving this repo and disabling renovate I'd like to get a brief note into the readme about the status of this repository.

Review Checklist

• [ ] Code contains useful comments
• [ ] (Integration-)Test cases added (or not applicable)
• [ ] Documentation added (or not applicable)
• [ ] Changelog updated (or not applicable)
• [ ] Cargo.toml only contains references to git tags (not specific commits or branches)
• [ ] Helm chart can be installed and deployed operator works (or not applicable)

Once the review is done, comment bors r+ (or bors merge) to merge. Further information

[soenkeliebau]

bors r+

[bors[bot]]

Pull request successfully merged into main.

Build succeeded:

• All tests passed