LibWeb: Move border width and color into LayoutStyle

To make this possible, I also had to give each LayoutNode a Document&
so it can resolve document-specific colors correctly. There's probably
ways to avoid having this extra member by resolving colors later, but
this works for now.

Libraries/LibWeb/Layout/LayoutListItemMarker.cpp

@@ -29,8 +29,8 @@
 
 namespace Web {
 
-LayoutListItemMarker::LayoutListItemMarker()
-    : LayoutBox(nullptr, StyleProperties::create())
+LayoutListItemMarker::LayoutListItemMarker(Document& document)
+    : LayoutBox(document, nullptr, StyleProperties::create())
 {
 }