Leverage existing shortcodes

[RichieEscarez]

Adopt existing OSS shortcodes to add content highlighting, like these callouts

Some how to info:

To create a shortcode for Knative, we need to add it into our site, here.

If we move forward with one of Istio's, we need copy their code (shortcode files), figure out what needs tweaking to get it to work as expected, test, and then we can start using that shortcode in our content.

Once its in, we should add it to our smoketest page