c0e0: Emoji reactions

FEP c0e0 describes the process by which Emoji reactions are implemented via the ActivityPub protocol.

There are several existing implementations already in-place.

Our implementation

NodeBB has not implemented this FEP at this time.

However, the existing functionality is present via nodebb-plugin-reactions, and this plugin would likely need to be updated or rewritten in order to support this FEP.