normalise import path in generated code

I have a project where the script running the code generation is a few levels deeper in the filesystem than the proto files that are being generated.

I end up with imports that look something like

`import * as ${PACKAGE} from '../../../../../some/very/long/file/path/${SERVICE}_pb';`

which can be normalised to

`import * as ${PACKAGE} from './${SERVICE}_pb';`

This would cause issues if my project was close enough to `/root` that the path becomes invalid

What can I do about this?