I think this idea is well-intentioned, but I can imagine that there will be quite a few people who would not appreciate this. Personally, I would just find it annoying if it happened to my code. Perhaps I was not planning on maintaining the code further, or perhaps I was already preparing the migration (!), or perhaps the code - while public - might not yet be releasable, or … (lots of other possible reasons). There is also quite a bit of orphaned code on the GitHub, and it’s not totally trivial to have a script decide whether a code base is orphaned/still maintained…
My principle would be: If you’re not a user/client/developer of a particular library or app, do not file issues/bugs/requests with it. And if you haven’t actually run into a particular issue, also don’t file issues.