Include doc build instructions for containerization

[jberendz]

URL of the document

https://github.com/theforeman/foreman-documentation/tree/master/guides#building-html-artifacts

Optional: Copy-paste the text you are reading

Describe the issue

Received request to include instructions on how to build containerized versions in guides readme.

Include example command such as make BUILD=katello-containerized under Building HTML Artifacts section.

Anything else to add? (context, suggestions for a fix, etc.)

[maximiliankolb]

I run the make commands in a container locally. You have to build a container image and tag it localhost/foreman-documentation:latest and then you can build each flavor as follows: $ podman run --rm -v ./:/foreman-documentation:Z localhost/foreman-documentation:latest make html BUILD=containerized-katello.

Note: It's containerized-katello, not katello-containerized, regardless of using containers or not.