expose own user on BaseRoom

so we don't have to pass session around everywhere we need this

src/matrix/room/BaseRoom.js

@@ -446,6 +446,10 @@ export class BaseRoom extends EventEmitter {
         return this._summary.data.membership;
     }
 
+    get user() {
+        return this._user;
+    }
+
     isDirectMessageForUserId(userId) {
         if (this._summary.data.dmUserId === userId) {
             return true;