https://github.com/eclipse/che/issues/19228

che-docs container is missing the dependency xmlstarlet to run "Validate Modular Docs".

Steps to reproduce

1. Open Che-docs on https://workspaces.openshift.com
2. Execute "Validate Modular Docs" on an asciidoc file
3. Terminal running in che-docs container displays the error:

Missing dependency – 'xmlstarlet'

Expected behavior

"Validate Modular Docs" executes properly.