docs: added feature flags docs (#2236)

www/docs/sidebars.js

@@ -232,6 +232,11 @@ module.exports = {
           id: "advanced/backend/migrations/index",
           label: "Create a Migration"
         },
+        {
+          type: "doc",
+          id: "advanced/backend/feature-flags/toggle",
+          label: "Toggle Feature Flags"
+        },
         {
           type: "doc",
           id: "advanced/backend/cron-jobs/create",