Compiler: compile jobs from typescript

[josephjclark]

Seems to me there's no reason we shouldn't support jobs written in typescript.

Given a flag or directive at the top of the job source, or a file extension, we should be able to first compile the job into javascript before running the regular transformation pipeline.

This is mostly not a very big deal - I guess the difficulty comes from setting up the typescript rules. Usually when we write typescript we provide a tsconfig. Would we have to default it? Should we accept one? What about type definitions, how do we import those?