LibWeb: Add window.sessionStorage

Author: https://github.com/paulwratt 🔰
Commit: 83eb5ac8fd
Pull-request: https://github.com/SerenityOS/serenity/pull/12926
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibWeb/HTML/Window.h

@@ -104,6 +104,7 @@ public:
     Selection::Selection* get_selection();
 
     RefPtr<HTML::Storage> local_storage();
+    RefPtr<HTML::Storage> session_storage();
 
     Window* parent();