LibHTML: Start building the style tree.

Walk the DOM and construct a parallel style tree that points back to the DOM
and has the relevant CSS property values hanging off of them.

The values are picked based on naive selector matching. There's no cascade
or specificity taken into account yet.

LibHTML/Dump.cpp

@@ -1,4 +1,5 @@
 #include <LibHTML/CSS/StyleSheet.h>
+#include <LibHTML/CSS/StyledNode.h>
 #include <LibHTML/DOM/Document.h>
 #include <LibHTML/DOM/Element.h>
 #include <LibHTML/DOM/Text.h>
@@ -67,6 +68,38 @@ void dump_tree(const LayoutNode& layout_node)
     --indent;
 }
 
+void dump_tree(const StyledNode& styled_node)
+{
+    static int indent = 0;
+    for (int i = 0; i < indent; ++i)
+        printf("    ");
+
+    String tag_name;
+    auto& node = *styled_node.node();
+    if (node.is_text())
+        tag_name = "#text";
+    else if (node.is_document())
+        tag_name = "#document";
+    else if (node.is_element())
+        tag_name = static_cast<const Element&>(node).tag_name();
+    else
+        tag_name = "???";
+
+    printf("%s", tag_name.characters());
+    printf("\n");
+
+    styled_node.for_each_property([&](auto& key, auto& value) {
+        for (int i = 0; i < indent; ++i)
+            printf("    ");
+        printf("  (%s: %s)\n", key.characters(), value.to_string().characters());
+    });
+    ++indent;
+    styled_node.for_each_child([](auto& child) {
+        dump_tree(child);
+    });
+    --indent;
+}
+
 void dump_rule(const StyleRule& rule)
 {
     printf("Rule:\n");