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.

Beginne mit der Guides-Seite unter material.angular.io/guides und sieh dir das zugehörige Angular Material rewrite issue, die verlinkten CDK-using libraries und die Videos an. Erstelle einen eigenständigen Getting Started with the CDK-Leitfaden für Bibliotheksentwickler, der nicht von Angular Material abhängt, nützliche Links enthält und von der Guides-Seite aus verlinkt ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.