Create a Getting Started Guide for the CDK

#### Documentation Feedback

The Angular Material Getting Started Guide is being re-written in https://github.com/angular/components/issues/16426.

It seems like a separate "Getting Started with the CDK" guide would be useful as well. It should primarily be focused on library developers and not depend upon Angular Material.

We have a number of projects that use the CDK that we could link to in addition to some useful videos for getting started.

Libraries using the CDK
- https://akveo.github.io/nebular/
- https://github.com/ng-lightning/ng-lightning
- https://github.com/NG-ZORRO/ng-zorro-antd
- https://github.com/primefaces/primeng
- https://github.com/Teradata/covalent
- https://github.com/positive-js/mosaic
- https://github.com/TemainfoSoftware/truly-ui
- https://barista.dynatrace.com/

CDK Videos
- https://www.youtube.com/watch?v=kYDLlfpTLEA
- https://www.youtube.com/watch?v=v__RuD9RX3I
- https://www.youtube.com/watch?v=4EXQKP-Sihw
- https://www.youtube.com/watch?v=ngyEpcwkLW0
- https://www.youtube.com/watch?v=b04UeKOcqCE
- https://www.youtube.com/watch?v=oz6qbOtEgNw
- https://www.youtube.com/watch?v=ejh_UVci9FA
- https://www.youtube.com/watch?v=ByK3t2-EbF0
- https://www.youtube.com/watch?v=aOPUvyrr3y4
- https://www.youtube.com/playlist?list=PLQpZdy2HZ5BQ3WF3Fa7HFgvMwxm7Ujr0h

**Affected documentation page:** Insert a link to the affected page on material.angular.io
https://material.angular.io/guides

Here's a [related Angular Blog post](https://blog.angular.io/angular-5-1-more-now-available-27d372f5eb4e) about the CDK.

Start with the guides page at material.angular.io/guides and review the related Angular Material rewrite issue, linked CDK-using libraries, and videos. Create a standalone Getting Started with the CDK guide for library developers that does not depend on Angular Material, incorporates useful links, and is linked from the guides page.

Written by the indexing model from the issue text.