Add support for typescript uniont types

[KJSanchez]

I'd like to be able to compile typescript union types. Something like what's below.

interface Bird {
  fly(): void;
  layEggs(): void;
}
 
interface Fish {
  swim(): void;
  layEggs(): void;
}

type Animal = Bird | Fish;

[adenh93]

Hey @KJSanchez,

Great feature request! I'll try to slot this in when I have a moment.

Currently raising a newborn while working full time, so can't be as active on this project as I'd like 😅

Thanks!