Bump to v0.8.7

Added

• delay_post mapping, for setting how long to wait (in seconds) between each post request to avoid hitting rate limits of the target Fediverse instance
• hashtags mapping (list), for filtering out tweets which don't match any of them
• tweet_ids mapping, for listing specific tweets to retrieve and post on the Fediverse account

Enhancements

• Provide a more meaningful exception message when an HTTP error code 422 is returned when updating the Fediverse profile
• Referenced more directly in the documentation the need to use an account ID instead of a username when targeting a Mastodon instance