Add Performance related settings

Integrates support for Feral Gamemode, discrete GPU support for Mesa and the proprietary Nvidia driver and MangoHud support

Signed-off-by: Jan200101 <sentrycraft123@gmail.com>

launcher/minecraft/MinecraftInstance.h

@@ -91,6 +91,7 @@ public:
 
     /// create an environment for launching processes
     QProcessEnvironment createEnvironment() override;
+    QProcessEnvironment createLaunchEnvironment() override;
 
     /// guess log level from a line of minecraft log
     MessageLevel::Enum guessLevel(const QString &line, MessageLevel::Enum level) override;