Fix GA for first page view (#5769)

src/pages/_app.tsx

@@ -15,6 +15,7 @@ import '../styles/sandpack.css';
 if (typeof window !== 'undefined') {
   if (process.env.NODE_ENV === 'production') {
     ga('create', process.env.NEXT_PUBLIC_GA_TRACKING_ID, 'auto');
+    ga('send', 'pageview');
   }
   const terminationEvent = 'onpagehide' in window ? 'pagehide' : 'unload';
   window.addEventListener(terminationEvent, function () {