feat(aio): page not found layout and designs (#16089)

Add 404 svg image
h1 custom styling

PR Close #16089

aio/content/file-not-found.md

@@ -1,3 +1,9 @@
-@title
 @description
-<h3>Document not found</h3>
+
+<div class="nf-container l-flex-wrap flex-center">
+    <img src="assets/images/support/angular-404.svg" width="300px" height="300px"/>
+    <div class="nf-response l-flex-wrap">
+        <h1>Page Not Found</h1>
+        <p>We're sorry. The page you are looking for cannot be found.</p>
+    </div>
+</div>