LibWeb: Implement Document's supported property names closer to the spec

Our implementation was errantly matching HTML tags other than the list
specified by the spec. For example, a <meta name=title> tag would be a
match for document.title.

For example, bandcamp will dynamically update its title when audio is
played as follows:

    document.title = "▶︎ " + document.title;

And bandcamp also has a <meta name=title> tag. The result was that the
title would become "▶︎ [object HTMLMetaElement]".

Tests/LibWeb/Text/input/DOM/Document-named-properties.html

@@ -5,6 +5,7 @@
 <img id="baz" src="http://www.example.com" alt="Example" />
 <form name="foo">
 </form>
+<meta name="kangaroo" />
 <script src="../include.js"></script>
 <script>
     test(() => {
@@ -41,5 +42,7 @@
         document.body.removeChild(document.greg);
 
         println(`no more greg or banana: ${document.greg === undefined}, ${document.banana === undefined}`);
+
+        println(`meta tag does not match: ${document.kangaroo === undefined}`);
     });
 </script>