WebSub support for RSS.chat
Previously we were only able to notify via rssCloud.
Now we also support WebSub because there are also a fair number of feed readers that only use WebSub.
We're using Andrew Shell's rsscloud.io as our WebSub hub, as we have for a long time with rssCloud.
Andrew please help us figure out if this is working correctly.
The source is in the repo, along with a worknote.