LibWeb: Add a very basic test for Text node APIs ("data" and "length")

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/99d81a5d499

Libraries/LibWeb/Tests/DOM/Text.js

@@ -0,0 +1,10 @@
+loadPage("file:///res/html/misc/blank.html");
+
+afterInitialPageLoad(() => {
+    test("Basic functionality", () => {
+        var title = document.getElementsByTagName("title")[0];
+        expect(title.firstChild.nodeName).toBe("#text");
+        expect(title.firstChild.data).toBe("Blank");
+        expect(title.firstChild.length).toBe(5);
+    });
+});