fix(docs-infra): fix Trusted Types violation in Analytics snippet (#42800)

The Google Analytics snippet loads its runtime by dynamically creating a
script element and assigning a URL to its src attribute. This causes a
Trusted Types violation.

To fix this, create an inline Trusted Types policy called 'aio#analytics'
to bless the script URL, which is a trusted constant.

PR Close #42800

aio/src/index.html

@@ -51,6 +51,12 @@
     // Note this is a customised version of the GA tracking snippet
     // See the comments below for more info
     (function (i, s, o, g, r, a, m) {
+      if (i.trustedTypes) {
+        // Specify path as a TrustedScriptURL when Trusted Types are available
+        g = i.trustedTypes.createPolicy('aio#analytics', {
+          createScriptURL: function (s) { return s; }
+        }).createScriptURL(g);
+      }
       i['GoogleAnalyticsObject'] = r; i[r] = i[r] || function () {
         (i[r].q = i[r].q || []).push(arguments)
       }, i[r].l = 1 * new Date(); a = s.createElement(o),