docs: initial content for references.d.ts

[rigor789]

We need to document more about @nativescript/types however I'm unsure whether or not it should be on the references.d.ts page here, or a separate page we link to from this page?

Curious about everyone's take on that /cc @NativeScript/tsc

[NathanWalker]

How about we include under the package.json since it is a dependency?

• references.d.ts
• package.json
  • @nativescript/core
  • @nativescript/types
  • @nativescript/webpack

Within project structure. The references.d.ts can be shown in the project structure but would jump to the @nativescript/types page to explain what they are and how/why references.d.ts plays into it.

[NathanWalker]

Reason for this is I recently brought up on TSC about moving away from global declares from types which would mean we could possibly move away from references.d.ts in the future - that way having it link to @nativescript/types page would work for now and future.