Add guide for render blocking JavaScript

content/guides.json

@@ -1,4 +1,13 @@
 [
+  {
+    "id": "avoid-render-blocking-javascript-with-async-defer",
+    "title": "Async and Defer Script Loading",
+    "description": "Learn how to avoid render blocking JavaScript using async and defer scripts.",
+    "isPro": false,
+    "authorUsername": "kamranahmedse",
+    "updatedAt": "2021-09-10T19:59:14.191Z",
+    "createdAt": "2021-09-10T19:59:14.191Z"
+  },
   {
     "id": "what-are-web-vitals",
     "title": "What are Web Vitals?",

content/guides/avoid-render-blocking-javascript-with-async-defer.md

@@ -0,0 +1,3 @@
+[![](/guides/avoid-render-blocking-javascript-with-async-defer.png)](/guides/avoid-render-blocking-javascript-with-async-defer.png)
+
+Here is the [original tweet](https://twitter.com/kamranahmedse/status/1436392322451841026) where this image was posted.