Add support for Activity Monitor

[theMikeD]

Description

WP Activity Log ( https://melapress.com/wordpress-activity-log/ ) is a plugin used to (you guessed it) track activity done in a site. It's able to track fields added to posts, but fields added elsewhere don't work. I have not done an exhaustive test, but fields added to terms don't register, and field on pages also created with FM are not tracked.

ETA
It looks like they have a system to create an extension, which is documented here https://melapress.com/support/kb/wp-activity-log-create-custom-events/ . There is one for ACF so I assume it would be similar to that.

Use Case

When a change is made to any field created by FM, it should appear in the activity log. This assists with error recovery and tracking.