Automatic progress updates

We only update the upstream social.popfeed.feed.listItem record in two scenarios:

• User presses "Sync progress now"
• User closes the current document

It would be helpful to add automatic syncing -- maybe at a periodic interval, or after a certain number of pages are turned, or something similar. The ability to toggle automatic tracking would be nice as well. The Hardcover plugin has toggleable automatic progress tracking, so that's probably a good reference.