添加调整焦点快捷键

src/action.h

@@ -6,3 +6,4 @@ void spawn(const user_action_arg_t *arg);
 void quit(const user_action_arg_t *arg);
 void select_tag(const user_action_arg_t *arg);
 void kill_client(const user_action_arg_t *arg);
+void focus_stack(const user_action_arg_t *arg);