#208: install Revisionary plugin for draft preview Revisions

Closes #208

To Review

[x] Checkout Branch.
[x] Run npm run local (or npm run refresh if you want a fresh database.)
[x] Go to http://the-world-wp.lndo.site/wp-admin.
[x] Ensure Faust settings are set to http://the-world-wp.lndo.site:3000 and frontend is running.

...then...

[x] Go to Revisions > Settings
[x] Under post types select (posts, pages, episodes)
[x] Under Scheduled Revisions uncheck update Published date
[x] Under Notifications set to never email editors (this is unnecessary)
[x] Save Settings
[x] Open any published story live frontend version in a new tab (and keep it open)
[x] In the admin, go to the posts page
[x] Click 'New revision' for that same published post
[x] change something.
[x] Save Draft
[x] Then Preview the draft, ensure you see the change
[x] Refresh the Live version, ensure it remains unchanged
[x] Publish the draft (confirm URL is unchanged)
[ ] Ensure changes show up in the live frontend version
[ ] Repeat for Episodes
[ ] Repeat for Pages