KeyboardMapper: Ask for unsaved changes on window close and file open

Author: https://github.com/krkk
Commit: b6510f8e76
Pull-request: https://github.com/SerenityOS/serenity/pull/12775

Userland/Applications/KeyboardMapper/KeyboardMapperWidget.h

@@ -25,6 +25,8 @@ public:
     void show_error_to_user(Error);
     void set_automatic_modifier(bool checked);
 
+    bool request_close();
+
 protected:
     virtual void keydown_event(GUI::KeyEvent&) override;
     virtual void keyup_event(GUI::KeyEvent&) override;