Review stale issues and PRs

The repository exhibits a few stale issues and PRs. For each of those decide between:
1. To maintain: the work will be continued (PR) or handled (issue)
2. To delete: the work is fully irrelevant/outdated and needs to be dropped entirely
3. To archive: the work is outdated, and will likely not be continued as is, but can still be relevant

Then, depending on the decision:
1. For maintained work, comment as to what work is required, make a statement about the state of the work
2. Close issues/PRs to be deleted, with a comment explaining why that is
3. Close issues/PRs to be archive, with a new issue related to that archived work, stating how it should be continued and why