LibWeb: Add LayoutRange::normalized()

We use this to ensure that we're always working with a selection where
the start() is before the end() in document order. That simplifies all
the logic around this.

Libraries/LibWeb/CMakeLists.txt

@@ -77,6 +77,7 @@ set(SOURCES
     Layout/LayoutListItem.cpp
     Layout/LayoutListItemMarker.cpp
     Layout/LayoutNode.cpp
+    Layout/LayoutPosition.cpp
     Layout/LayoutReplaced.cpp
     Layout/LayoutTable.cpp
     Layout/LayoutTableCell.cpp