Add ClientOptions.restTimeOffset for better performance for bots with a good network connection

src/util/Constants.js

@@ -20,6 +20,8 @@ exports.Package = require('../../package.json');
  * @property {boolean} [sync=false] Whether to periodically sync guilds (for userbots)
  * @property {number} [restWsBridgeTimeout=5000] Maximum time permitted between REST responses and their
  * corresponding websocket events
+ * @property {number} [restTimeOffset=500] The extra time in millseconds to wait before continuing to make REST
+ * requests (higher values will reduce rate-limiting errors on bad connections)
  * @property {WSEventType[]} [disabledEvents] An array of disabled websocket events. Events in this array will not be
  * processed, potentially resulting in performance improvements for larger bots. Only disable events you are
  * 100% certain you don't need, as many are important, but not obviously so. The safest one to disable with the
@@ -38,6 +40,7 @@ exports.DefaultOptions = {
   sync: false,
   restWsBridgeTimeout: 5000,
   disabledEvents: [],
+  restTimeOffset: 500,
 
   /**
    * Websocket options. These are left as snake_case to match the API.