Update indexing to support new definition format

[blakeembrey]

See DefinitelyTyped/DefinitelyTyped#15367 (comment). Looks like everything has been moved under types. Should probably just strip types/ from the prefix of names when it exists in the diff. Need to support both formats, just as with the index.d.ts transition, to support re-indexing of older content. Perhaps it could also switch on commit (though it appears they may force push this as some point, so probably avoid it) or timestamp. Otherwise, I'll just pray no .d.ts files get added outside for now and re-visit in the future.