Implement mainwindow example

Sine Striker

2023-12-05 f8975a7d449bac21a2fdbc1a8ca85d1f5b99b362

 src/core/contexts/win32windowcontext.cpp

@@ -266,7 +266,7 @@
            case HTBORDER:
                return Win32WindowContext::FixedBorder;
            default:
                break;
                break; // unreachable
        }
        return Win32WindowContext::Outside;
    }
@@ -1165,6 +1165,8 @@
                                break;
                            case CoreWindowAgent::Unknown:
                                break;
                            default:
                                break; // unreachable
                        }
                    }
                    if (*result == HTNOWHERE) {