Add Safari internal JS services and documentation

js/search/OpenSearchURLFinder.js

@@ -0,0 +1,22 @@
+//# sourceURL=__InjectedScript_OpenSearchURLFinder.js
+/* Copyright (c) 2025 Apple Inc. All rights reserved. */
+var OpenSearchURLFinder = function () {};
+OpenSearchURLFinder.prototype = {
+  firstOpenSearchURLString: function () {
+    if (!document.head) return null;
+    for (
+      var e = document.head.getElementsByTagName("link"), r = e.length, n = 0;
+      n < r;
+      ++n
+    ) {
+      var t = e[n];
+      if (
+        "search" === t.getAttribute("rel") &&
+        "application/opensearchdescription+xml" === t.getAttribute("type")
+      )
+        return t.href;
+    }
+    return null;
+  },
+};
+var OpenSearchURLFinderJS = new OpenSearchURLFinder();