Add support for content snippets within quick start tasks

[jbyrne-redhat]

WHAT
Add support for content snippets within quick start tasks.

WHY
In Managed Application Services (MAS), lots of our quick starts have steps in common. For example, several quick starts use the same set of instructions for creating a Kafka topic. Ideally, we could single-source these common steps using a reusable content snippet that we would include in each applicable quick start. That is just one example, and other opportunities for reuse exist in our quick starts. Similarly, there are plenty of opportunities for content reuse in the non-quick-start documentation that we publish on the Red Hat Customer Portal.

I've already done some work on my fork to test the use of a shared content directory in the app-services-guides repo. For example, the following links show two standard Asciidoc include statements that include the same snippet of content (from a shared-content directory) in two different guides:

• https://github.com/jbyrne-redhat/app-services-guides/blob/shared-content-test/docs/kafka/quarkus-kafka/README.adoc?plain=1#L186
• https://github.com/jbyrne-redhat/app-services-guides/blob/shared-content-test/docs/kafka/nodejs-kafka/README.adoc?plain=1#L201

My testing shows that with some coding additions to our mod docs build scripts, we can make this approach work for the modular documentation that the Asciidoc splitter tool generates from our README.adoc files.

However, when I test generation of our console quick starts from the same README files, I see that Patternfly cannot handle the type of include statements shown above. That is a significant blocker to progressing with content reuse in the app-services-guides repo.