docs: include unofficial AngularJS Material typings

[Splaktar]

Proposal:

Include unofficial AngularJS Material TypeScript typings (https://www.npmjs.com/package/@types/angular-material) in the docs site.

What is the use-case or motivation for changing an existing behavior?

While not officially supported, it would certainly be good to let people know that it exists and is used by many projects (3,212 downloads a week).

Which versions of AngularJS, Material, OS, and browsers are affected?

N/A

Is there anything else we should know? Stack Traces, Screenshots, etc.

N/A

[Splaktar]

For anyone looking to update these types, you can find them here (https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/angular-material/index.d.ts) and send a PR to that repo.