feature request: Run transformers if --noEmit #178

Seems typescript itself runs the custom transforms as part of the emit which prevents transformers being used called at all. I'd like to execute my transformers even with --noEmit to do some validations:

https://github.com/microsoft/TypeScript/blob/c85e626d8e17427a6865521737b45ccbbe9c78ef/src/compiler/program.ts#L2765-L2772

Hence it would be great if ts-patch could ensure that the transformers are still called. The easiest solution could be to pass use a custom CompilerHost forwarding all calls to the original one. Then in the writeFile check for options.noEmit.

The alternative to call the transformers within ts-patch seems like an overkill as the logic is quite complex inside typescript.