LibWeb: Wire up UniversalGlobalScopeMixin to ShadowRealmGlobalScope

Author: https://github.com/shannonbooth
Commit: 457cdd0cc3
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2220
Reviewed-by: https://github.com/ADKaster ✅

Tests/LibWeb/Text/input/HTML/shadow-realm-btoa.html

@@ -0,0 +1,8 @@
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        const realm = new ShadowRealm();
+        const result = realm.evaluate(`() => self.btoa('Hello, world!')`)();
+        println(`Shadow realm evaluation returned: ${result}`);
+    });
+</script>

Tests/LibWeb/Text/input/HTML/shadow-realm-url.html

@@ -0,0 +1,8 @@
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        const realm = new ShadowRealm();
+        const result = realm.evaluate(`() => new URL('https://example.com/path?name=value').hostname`)();
+        println(`Shadow realm evaluation returned: ${result}`);
+    });
+</script>