Language generation with torchscript model?

@laphangho Good luck!

To add a little more context: SageMaker wants a ScriptModule, not trace. Trace is not possible with .generate(), but script works fine. And to use script mode, saving the model in a different way (than the default .save_pretrained() method is not required since torchscript=True can simply be provided as an additional argument when creating the model object.