add voice region getting (#1108)

* add voice region getting

* clean up this mess

* add docstrings

* Update VoiceRegion.js

* Update RESTMethods.js

src/structures/Guild.js

@@ -322,6 +322,14 @@ class Guild {
     return this.client.rest.methods.getGuildWebhooks(this);
   }
 
+  /**
+   * Fetch available voice regions
+   * @returns {Collection<string, VoiceRegion>}
+   */
+  fetchVoiceRegions() {
+    return this.client.rest.methods.fetchVoiceRegions(this.id);
+  }
+
   /**
    * Fetch a single guild member from a user.
    * @param {UserResolvable} user The user to fetch the member for