LibHTML: Start fleshing out a StyleResolver class.

This will be responsible for matching selectors and creating LayoutStyle
objects for the document and its elements.

LibHTML/CSS/StyleResolver.cpp

@@ -0,0 +1,23 @@
+#include <LibHTML/CSS/StyleResolver.h>
+#include <LibHTML/CSS/StyleSheet.h>
+
+StyleResolver::StyleResolver(Document& document)
+    : m_document(document)
+{
+}
+
+StyleResolver::~StyleResolver()
+{
+}
+
+OwnPtr<LayoutStyle> StyleResolver::resolve_document_style(const Document& document)
+{
+    UNUSED_PARAM(document);
+    return nullptr;
+}
+
+OwnPtr<LayoutStyle> StyleResolver::resolve_element_style(const Element& element)
+{
+    UNUSED_PARAM(element);
+    return nullptr;
+}