Describe the bug

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

Che version

• latest
• nightly
• other: please specify

Steps to reproduce

1. Open Che-docs on https://workspaces.openshift.com
2. Execute "Validate Modular Docs" on an

Document the commands that clients should implement and their expected behaviour on https://github.com/eclipse/eclipse.jdt.ls/wiki/JDT-LS-Extensions

Consider the following:

void meth(Closure closure) {
  closure.|
}

When invoking content assist (Ctrl+Space) at |, the methods and properties of groovy.lang.Closure are very low in the list of proposals. This is due to very-well-known type adjustments made within org.codehaus.groovy.eclipse.codeassist.proposals.AbstractGroovyProposal.getRelevanceClass().