Ladybird: Rudimentary tabbed browsing support

This patch removes the browser WebView from the window and places it
inside a Tab object, all wrapped up in a QT tab control. So far you can
create tabs, but can't close them.

Ladybird/CMakeLists.txt

@@ -37,6 +37,7 @@ set(SOURCES
     RequestManagerQt.cpp
     main.cpp
     WebView.cpp
+    Tab.cpp
 )
 
 add_executable(ladybird ${SOURCES})