feat(typescript-plugins): use babel to transpile .ts plugins

[eventualbuddha]

Fixes #51 and supersedes #57. The gist of this is that I updated the babel dependencies from 6.x to 7.x, which adds support for transpiling TypeScript. I ended up writing my own @babel/register-alike to make it easier to support both .js files and .ts files.

cc @mcMickJuice @hzoo

[eventualbuddha]

All this stuff moved into RecastPlugin since parser and generator options are now handled by plugin hooks.

[hzoo]

I ended up writing my own @babel/register-alike to make it easier to support both .js files and .ts files.

I think if the functionality is missing we should modify register in a similar way if possible @loganfsmyth

[eventualbuddha]

I expect it might be possible to use @babel/preset-typescript and @babel/preset-env even with .js files and have it work. Maybe I’ll just do that.

[eventualbuddha]

Actually, the main issue I had was that ignore and only were getting set even when I didn't provide them. I think the workaround would be for me to specify both of them like so:

  ignore: [/node_modules/],
  only: [/.*/]

By default you end up with ignore and only that restrict it to the current working directory and not node_modules, which might be fine except that remote plugins get downloaded to a temp directory which could be anywhere. I'm happy to use @babel/register instead if it doesn't require too much futzing to get it working. Using pirates directly is pretty clean, except that I have to hardcode the list of extensions.