Add an ES6 lib.webworker.d.ts

[bwalderman]

I ran into this when I tried to use ES6 features in a web worker script. The lib typings do not yet include an ES6 version of lib.webworker.d.ts. This makes it difficult to target ES6 for a project meant to run in a web worker.

As a workaround, I created lib.webworker.es6.d.ts which is a copy of the original that references lib.core.es6.d.ts instead of lib.core.d.ts. The permanent fix should be to generate this with the rest of the typings in the Jakefile.

[yuit]

We will fix this using library modularization. With the new flag --lib, to use both web-worker and es6, one can just do --lib webworker es6. So we will not generating the new combining lib file

[mhegazy]

This should be fixed by #7715. --lib support should be available now in typescript@next and in the next TypeScript release.