[NEOS-1237] Add github action that prevents merge on unlabeled PRs

[nickzelei]

We should have a job that runs on a pull request that does not contain any labels (or maybe just always runs).

Then we can add a condition that it is unmergeable if it does not have a label attached.

We might need it to run all the time os that we can can "require" the test be passing before it is considered mergeable.

Could maybe be used as a reference: https://stackoverflow.com/questions/71502652/prevent-merging-of-branch-conditionally-based-on-label

This way it forces us to label or PRs so that they are better associated in our changelog.

_{From SyncLinear.com | NEOS-1237}

[frankie-mur]

Heya @nickzelei , I could take this on 🫡

[nickzelei]

Heya @nickzelei , I could take this on 🫡

Sounds good!