defer loading of external contents

_includes/header.html

@@ -151,4 +151,31 @@
   <meta name="theme-color" content="#ffffff">
 
   <link rel="stylesheet" href="/assets/css/style.css" />
+  <script>
+    function prepareCodersrank() {
+      var placeholders = document.getElementsByClassName("cr-placeholder");
+      console.log(placeholders);
+      if (localStorage.getItem("load-codersrank")) {
+        loadCodersrank();
+      } else {
+        for (ph of placeholders) {
+          ph.addEventListener("click", e => {
+              e.preventDefault();
+              console.log(e);
+            localStorage.setItem("load-codersrank", true);
+            loadCodersrank();
+          });
+        }
+      }
+    }
+
+    function loadCodersrank() {
+      var script = document.createElement("script");
+      script.src = "https://unpkg.com/@codersrank/activity/codersrank-activity.min.js";
+      for (ph of document.getElementsByClassName("cr-placeholder")) {
+        ph.parentElement.innerHTML = ph.childNodes[0].data;
+      }
+      document.head.appendChild(script);
+    }
+  </script>
 </head>