Add special alert for throttled requests (#11677)

* Add special alert for throttled requests

* Use an extra attribute instead of an array

app/javascript/mastodon/selectors/index.js

@@ -128,6 +128,7 @@ export const getAlerts = createSelector([getAlertsBase], (base) => {
   base.forEach(item => {
     arr.push({
       message: item.get('message'),
+      message_values: item.get('message_values'),
       title: item.get('title'),
       key: item.get('key'),
       dismissAfter: 5000,