LEKTORD: Set the main window icon

lektord/c/mainwindow.cc

 #include "mainwindow.hh"
+#include "icon.xpm"
 
 MainWindow::MainWindow(module_qt_window_s *qt_window, QWidget *parent) noexcept
     : QMainWindow(parent)
 {
+    setWindowIcon(QIcon(QPixmap(icon)));
     this->mpv             = new MpvWidget(&(qt_window->launched), this);
     qt_window->mpv_widget = this->mpv;
     connect(this->mpv, &MpvWidget::titleChanged, this, &MainWindow::updateWindowTitle);