LibWeb: Start implementing basic JavaScript DOM bindings

This patch introduces the Wrapper and Wrappable classes.

Node now inherits from Wrappable, and can be wrapped in a GC-allocated
Bindings::NodeWrapper object. The only property we expose right now is
the very simple nodeName property.

When a Document's JS::Interpreter is first instantiated, we add a
"document" property with a DocumentWrapper object to the global object.

This is pretty cool! :^)

Libraries/LibWeb/Bindings/NodeWrapper.cpp

@@ -0,0 +1,20 @@
+#include <LibJS/PrimitiveString.h>
+#include <LibJS/Value.h>
+#include <LibWeb/Bindings/NodeWrapper.h>
+#include <LibWeb/DOM/Node.h>
+
+namespace Web {
+namespace Bindings {
+
+NodeWrapper::NodeWrapper(Node& node)
+    : m_node(node)
+{
+    put("nodeName", JS::js_string(heap(), node.tag_name()));
+}
+
+NodeWrapper::~NodeWrapper()
+{
+}
+
+}
+}