Enhancement: Add typings to distributed package

Created by: e-avidan

According to the TypeScript npm publishing guidelines, a publisher of a package may include the d.ts file in the distributed package.

The DashJS package already does so, but there are a few things missing:

• MUST include a "types" fields in the package.json file, similar to a "main" field
• MAY include it in the 'build' and 'dist' folders, for the sake of completeness

In order to do so the package.json needs to be updated, and also the copy task in the gruntfile