Use Segoe UI font on Windows.

Qt uses "MS Shell Dlg 2" as the default font, which resolves to
Tahoma and not Segoe UI, which is the actual Windows 10 default font.

See QTBUG-58610

src/core/Bootstrap.cpp

@@ -73,7 +73,6 @@ namespace Bootstrap
 
         setupSearchPaths();
         applyEarlyQNetworkAccessManagerWorkaround();
-        Translator::installTranslators();
     }
 
     /**
@@ -84,6 +83,15 @@ namespace Bootstrap
     void bootstrapApplication()
     {
         bootstrap();
+        Translator::installTranslators();
+
+#ifdef Q_OS_WIN
+        // Qt on Windows uses "MS Shell Dlg 2" as the default font for many widgets, which resolves
+        // to Tahoma 8pt, whereas the correct font would be "Segoe UI" 9pt.
+        // Apparently, some widgets are already using the correct font. Thanks, MuseScore for this neat fix!
+        QApplication::setFont(QApplication::font("QMessageBox"));
+#endif
+
         MessageBox::initializeButtonDefs();
 
 #ifdef Q_OS_MACOS