LibWeb+WebContent: Label redirects with new FrameLoader::Type::Redirect

Previously we labeled redirects as normal FrameLoader::Type::Navigation,
now we introduce a new FrameLoader::Type::Redirect and label redirects
with it. This will allow us to handle redirects in the browser
differently (such as for overwritting the latest history entry when a
redirect happens) :^)

Userland/Libraries/LibWeb/Loader/FrameLoader.h

@@ -21,6 +21,7 @@ public:
         Navigation,
         Reload,
         IFrame,
+        Redirect,
     };
 
     static void set_default_favicon_path(String);