types(Partial): add partial reactions (#6066)

Co-authored-by: Noel <buechler.noel@outlook.com>

src/structures/DMChannel.js

@@ -16,8 +16,10 @@ class DMChannel extends Channel {
    */
   constructor(client, data) {
     super(client, data);
+
     // Override the channel type so partials have a known type
     this.type = 'DM';
+
     /**
      * A manager of the messages belonging to this channel
      * @type {MessageManager}