fix typescript config for rollup

[cellog]

This allows files other than index.ts to be in typescript

[nickserv]

As far as I'm aware, we don't need this since the existing Rollup config in ts-conversion already compiles TypeScript to JavaScript. If files other than index.ts aren't working, then ts needs to be added to Rollup's extensions. Types can be checked with npm install, npm publish, or npm run check-types.

[cellog]

as much as I would like to not need this, rollup does not recognize import 'blah' if blah is in blah.ts (feel free to prove me wrong, I would much rather not have to do this)

[nickserv]

I fixed this by using rollup-plugin-node-resolve: #3517

[cellog]

closing as obsolete, thanks @nickmccurdy !

[cellog]

re-opening, the fix doesn't quite work as the ES and CommonJS builds don't use nodeResolve

[cellog]

bye again