Add TODO compile var + Fix doxygen issue

You can make your code warn on compile time for the TODO's
In order to do so, uncomment the following line. in pro file
DEFINES += TODO_LIST

sources/ui/bomexportdialog.cpp

@@ -83,7 +83,9 @@ int BOMExportDialog::exec()
 #if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)	// ### Qt 6: remove
 				stream << getBom() << endl;
 #else
+#if TODO_LIST
 #pragma message("@TODO remove code for QT 5.15 or later")
+#endif
 				stream << getBom() << &Qt::endl(stream);
 #endif
 			}