app.gainforest.feed.like

Record declaring a 'like' of a piece of subject content. A faithful port of app.bsky.feed.like into the app.gainforest.feed namespace. `subject` is a com.atproto.repo.strongRef (uri + cid), so a like can target any record in the GainForest commons — an observation, project, cert, organization, donation, post, or comment — and the GainForest appview decides which subject types to aggregate. Unlike = delete this record.