Check if hashtag_helper.py works with Mastodon

The hashtag helper bot is only verified to work with a Pleroma instance as the destination for the toots it discovers.

Basically, "searching" for toots by URL on Pleroma, is enough to pull them into the Federated timeline and make them searchable. That is how the bot works. I don't know if Mastodon has the same behaviour.

This needs testing. Volunteers welcome!