Support babel 7 for .ts / .tsx

[simonbuchan]

Mentioned this in #47, but got no reply. Babel 7 adds @babel/preset-typescript, which, obviously, lets you transpile .ts/.tsx code with the babel pipeline (with some limitations). It would be good to be able to use, e.g. webpackfile.ts without adding any more dependencies or workarounds.

Looks simple enough to add - just add @babel/register with extensions: '.ts' to the end of .ts - but I'd like feedback on if this is a terrible idea before submitting a PR 🤞

[phated]

I'm not a big fan of this idea. But if we do it, I'd want babel to be the last one in the list (excluding deprecated ones)

[simonbuchan]

Yeah, you very well could be using both ts-node for .ts and babel 7 for .babel.js. Hah, .babel.ts?

[phated]

Unfortunately "double" extensions don't work correctly. I think there's an issue about that.