Quickstart misses scroll indicator shadow

Description of problem:

The QuickStart content shows a shadow above and/or below the content when the user can scroll into that direction. This feature is missing now.

Prerequisites (if any, like setup, operators/versions):

None

Steps to Reproduce

1. Open a quick start
2. Reduce the window so that the content of the quick start is scrollable.

Actual results:

No shadow when the user can scroll the content into the content direction.

Expected results:

A shadow when the user can scroll the content into the content direction.

Reproducibility (Always/Intermittent/Only Once):

Always

Build Details:

4.9 (tested on master 2860e58114b4f811ac2ebf6ce34dd99263920e17)

Additional info:

Quick start is now extracted into PatternFly