paterns_menu: Move it to it's own class

includes/context.hpp

@@ -21,6 +21,7 @@ class SettingsMenu;
 class SelectionMenu;
 class ControlMenu;
 class Selection;
+class PaternsMenu;
 
 typedef struct ctx {
   std::shared_ptr<World> world = nullptr;
@@ -30,6 +31,7 @@ typedef struct ctx {
   std::shared_ptr<SelectionMenu> selection_menu = nullptr;
   std::shared_ptr<ControlMenu> control_menu = nullptr;
   std::shared_ptr<Selection> selection = nullptr;
+  std::shared_ptr<PaternsMenu> paterns_menu = nullptr;
   nlohmann::json config_json;
 } ctx;