LibWeb: Fire navigation event as required in History.pushState()

Author: https://github.com/awesomekling
Commit: a1519e67fb
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/993

Tests/LibWeb/Text/input/HTML/pushState-navigation-event.html

@@ -0,0 +1,14 @@
+<script src="../include.js"></script>
+<script>
+    asyncTest((done) => {
+        let handler = function() {
+            println("PASS");
+
+            window.navigation.removeEventListener("navigate", handler);
+            history.pushState({}, null, "pushState-navigation-event.html");
+            done();
+        };
+        window.navigation.addEventListener("navigate", handler);
+        history.pushState({}, null, "?ok");
+    });
+</script>