org.simocracy.feed.like

Record declaring a 'like' of a piece of subject content. A port of app.bsky.feed.like (via app.gainforest.feed.like) into the org.simocracy.feed namespace. `subject` is a com.atproto.repo.strongRef (uri + cid), so a like can target any record in the Simocracy commons — a proposal, sim, gathering, decision, skill, post, or comment — and the Simocracy appview decides which subject types to aggregate. Unlike = delete this record.