Feature request: post updated entries

[bkil]

The bot only posts new entries at the moment. Some systems generate a feed with updates edited into the body of a given entry (usually the last one). For example:

• https://status.matrix.org/feed.atom

To avoid possible flooding due to backend bugs, we might want to limit this functionality to the most recent entry (or to at most one updated entry per poll or only allow updates for 1 week, etc.).