fix: messageReactionRemove not emitting for partial messages (#3125)

src/client/actions/MessageReactionAdd.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const Action = require('./Action');
+const { Events } = require('../../util/Constants');
 
 /*
 { user_id: 'id',
@@ -31,6 +32,14 @@ class MessageReactionAdd extends Action {
       me: user.id === this.client.user.id,
     });
     reaction._add(user);
+    /**
+     * Emitted whenever a reaction is added to a cached message.
+     * @event Client#messageReactionAdd
+     * @param {MessageReaction} messageReaction The reaction object
+     * @param {User} user The user that applied the guild or reaction emoji
+     */
+    this.client.emit(Events.MESSAGE_REACTION_ADD, reaction, user);
+
     return { message, reaction, user };
   }
 }