use nvidia graphics automatically on laptops with optimus

src/citra_qt/main.cpp

@@ -54,6 +54,12 @@
 Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin);
 #endif
 
+#ifdef _WIN32
+extern "C" {
+__declspec(dllexport) unsigned long NvOptimusEnablement = 0x00000001;
+}
+#endif
+
 /**
  * "Callouts" are one-time instructional messages shown to the user. In the config settings, there
  * is a bitfield "callout_flags" options, used to track if a message has already been shown to the