Improve workflow-run RO-Crates created by Galaxy

[stain]

It follows it just about by letter, to verify if it goes through the validator, but needs more to get into the spirit of Workflow Run RO-Crate.

[stain]

Oliver to list in this issue what are the current work, then make smaller issues upstream to discuss with Galaxy team.

[OliverWoolland]

The first tasks are to

• Add tests which use the RO Crate validator to assert that the WRROCs generated by Galaxy are valid
• Modify the RO Crate generation functionality to allow the above tests to pass
• Prepare a PR for this

Then the work would be to proceed to meet the spec for Process run and Workflow run crates