feat: add Vercel Web Analytics

Add analytics tracking to all documentation pages using docmd's
customJs configuration. The script dynamically loads Vercel's
analytics from /_vercel/insights/script.js.

- Create assets/js/vercel-analytics.js initialization script
- Add customJs config to docmd.config.js

Author: marklearst

assets/js/vercel-analytics.js

@@ -0,0 +1,15 @@
+// Vercel Web Analytics initialization
+// https://vercel.com/docs/analytics
+window.va =
+  window.va ||
+  function () {
+    (window.vaq = window.vaq || []).push(arguments);
+  };
+
+// Dynamically load the Vercel Analytics script
+(function () {
+  var script = document.createElement('script');
+  script.defer = true;
+  script.src = '/_vercel/insights/script.js';
+  document.head.appendChild(script);
+})();

docmd.config.js

@@ -23,6 +23,7 @@ module.exports = {
   },
   autoTitleFromH1: true,
   copyCode: true,
+  customJs: ["/assets/js/vercel-analytics.js"],
   navigation: [
     { title: "Home", path: ".", icon: "home" },
     {