Document how to use the 'role' in the CLI command
Document how to use the 'role' in the CLI command

It's not a direct mapping, so I've added some instruction for this, and also a brief
explanation about the `-l` parameter.
alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs