Refactor calendar widget changes

assets/toc.js

@@ -9,7 +9,7 @@
   nav.className = "toc";
 
   var header = document.createElement("div");
-  header.className = "toc-header";
+  header.className = "panel-header";
   header.textContent = "Contents";
   nav.appendChild(header);
 
@@ -28,7 +28,7 @@
 
   var toggle = document.createElement("button");
   toggle.type = "button";
-  toggle.className = "toc-toggle";
+  toggle.className = "panel-toggle";
   toggle.textContent = "Contents";
   toggle.setAttribute("aria-expanded", "false");
   toggle.addEventListener("click", function () {