add a user_id field to Message Reaction Remove All event

[3yal]

Staff members like to troll, it happens frequently and message reactions are somewhat important in some servers. Having a new AuditLogEvent for this or just adding the user_id field would help a ton

[vakiliner]

I don't think adding an AuditLogEvent is a good idea, as it will clutter the logs
But adding a new field, user_id (or more precisely moderator_id, since user_id already exists in MessageReactionRemove) to the Gateway event seems like a better idea