Add logging for patterns and flags

[coreymckrill]

This enables the new logging feature in the Internal Notes plugin for the Pattern post type, and adds some custom logging for when a pattern gets flagged and when flags are managed by moderators.

This wraps up #57, albeit in a slightly different way than originally imagined. There are probably still some workflow improvements that could be made around reviewing flags, but this is an MVP, and we can iterate once we have a better idea of how pattern moderation is going to play out.

Fixes #57

Screenshot

How to test the changes in this Pull Request:

1. Create a new pattern. Then edit the pattern.
2. View the pattern on the front end. Click the "Report this pattern" button and submit a flag.
3. In WP Admin, go to Block Pattern > All Flags. Mark the flag as resolved.
4. Now view the Edit screen in WP Admin for the pattern. Open the Notes sidebar. All of your previous activity should be recorded in log entries.

[ryelle]

Looks good, I see all the post change logs & the flag messages 👍🏻