Reference index.d.ts types in package.json

[peterharding]

As recommended in http://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html,
the package.json should contain a reference to the type declarations file index.d.ts.

In addition to being best practice, it avoids some potential problems:

Without this reference, someone could have a project with the following tsconfig.json:

"compilerOptions": {
    "moduleResolution": "node",
    "strictNullChecks": true
  },
  "exclude": [
    "node_modules"
  ]

Currently, if any file in their project has import { deserialize } from "json-typescript-mapper";, then json-typescript-mapper/index.ts will not be excluded by tsc. Therefore, when compiling their project with strictNullChecks: true, json-typescript-mapper/index.ts will be be incorrectly checked by tsc, and generate the following errors:

node_modules/json-typescript-mapper/index.ts(133,48): error TS2345: Argument of type '(new () => {}) | undefined' is not assignable to parameter of type 'new () => {}'.
  Type 'undefined' is not assignable to type 'new () => {}'.
node_modules/json-typescript-mapper/index.ts(163,9): error TS2322: Type 'undefined' is not assignable to type 'T'.
node_modules/json-typescript-mapper/index.ts(170,9): error TS2322: Type 'undefined' is not assignable to type 'T'.

Adding the index.d.ts reference to package.json allows tsc to correctly ignore json-typescript-mapper.

[peterharding]

Just noticed that http://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html has:

Also note that if your main declaration file is named index.d.ts and lives at the root of the package (next to index.js) you do not need to mark the "types" property, though it is advisable to do so.

Strangely, this must not be working for me, since adding the types reference prevented my compile errors.