Improvement: handle stale issues and prs

[AndreasBoehm]

Example output can be found here under Run actions/stale@v9

Statistics:

Processed items: 90
├── Processed issues: 74
└── Processed PRs   : 16
New stale issues: 34
Added issues labels: 34
Added issues comments: 34
Fetched items: 90
Fetched items events: 34
Fetched items comments: 34
Operations performed: 138

Once we agree on the config i will update the stale-action within repo-maintenance.yml and mark this PR as ready.

[AndreasBoehm]

@schlimmchen Let's discuss the settings on which i commented.

[schlimmchen]

Are these the steps to perform before merging this?

1. Add one of the labels to all open issues that we think should stay open.
2. Remove the TODOs from the YAML.
3. Remove the "debug" setting from the YAML.

[AndreasBoehm]

All three steps are valid but there is one more thing todo.
The first two steps are valid.
I already removed 'debug'

Remove the stale step from its current file and adjust the existing stale action here instead: https://github.com/hoylabs/OpenDTU-OnBattery/blob/development/.github/workflows/repo-maintenance.yml#L21

I only added it to the current file to be able to test it.