Show workflow license

[stain]

Description

Display link to the workflow's declared license. If none is declared, check for LICENSE or LICENSE.txt.

Motivation and Context

As pointed out in #183 we don't render the license. From #180 this uses schema:license with a fallback to doap:license and dcterms:license, assuming it is a URI.

How Has This Been Tested?

Tested with workflows:

• https://github.com/EBI-Metagenomics/ebi-metagenomics-cwl/blob/master/tools/collate_unique_SSU_headers.cwl
• https://github.com/common-workflow-language/workflows/blob/master/workflows/hello/hello.cwl
• https://github.com/FarahZKhan/ebi-metagenomics-cwl/blob/master/workflows/rna-selector.cwl

Screenshots (if appropriate):

In same order:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.