LibGUI: Automatically scroll to a new column on adding it in ColumnsView

Author: https://github.com/krkk
Commit: 70885a3dee
Pull-request: https://github.com/SerenityOS/serenity/pull/16700

Userland/Libraries/LibGUI/AbstractScrollableWidget.h

@@ -56,6 +56,7 @@ public:
 
     void scroll_to_top();
     void scroll_to_bottom();
+    void scroll_to_right();
     void update_scrollbar_ranges();
 
     void set_automatic_scrolling_timer_active(bool);