refactor: move Guild#defaultRole to RoleStore#everyone (#3347)

* remove guild#defaultRole

* add RoleStore#defaultRole

* typings

* fix trailing space

* another one

* Rename it to everyone

src/stores/RoleStore.js

@@ -110,6 +110,15 @@ class RoleStore extends DataStore {
     });
   }
 
+  /**
+   * The `@everyone` role of the guild
+   * @type {?Role}
+   * @readonly
+   */
+  get everyone() {
+    return this.get(this.guild.id) || null;
+  }
+
   /**
    * The role with the highest position in the store
    * @type {Role}