problem with typescript base package resolution

Hi there,

first of all thanks for this library - the others who claim to do the same have driven me crazy!

I have a minor problem with using the standard es2015 libraries delivered with TypeScript though.

I have to write the exact name of the library file as included in the TypeScript package like this:

tsconfig.json

  "compilerOptions": {
    "target": "es5",
    "experimentalDecorators": true,
    "lib": [
      "lib.es2015.d.ts" << this is the exact file name
    ]
  }

Just for the record - the file in question can be found in node_modules/typescript/lib/lib.es2015.d.ts.

But the correct syntax would be like this:

tsconfig.json

  "compilerOptions": {
    "target": "es5",
    "experimentalDecorators": true,
    "lib": [
      "es2015"
    ]
  }

Reproduce the issue with the shown tsconfig.json, comparing "lib.es2015.d.ts" with the expected "es2015" identifier and the TypeScript package under node_modules/typescript/lib. Locate the package-resolution entry point and existing tests, then verify that the shorter library name resolves while the current syntax continues to work.