Provide a filter to allow modifying the notified post format

[medfreeman]

I'd have a need for the post format to be modified prior to notification.
I have to add specific metadata that obviously can't be added atm (or here, but the body key value has to be json_decoded and re-encoded).

That would imply wrapping these lines in a filter call.
It should provide the post ID or object, and the actual array.
A good name could be 'jras_notification_format_post' ?

or could i use standard rest api hooks ? It seems not but i don't have an extensive knowledge of the API atm.

[tlovett1]

Filter PR would be fine.