[Signing 2] Add download signature item

[brumik]

[himdel]

the expand signature button works, but the signature is mistreating whitespace, I think you need white-space: pre; (or pre-wrap) on that element: (there should be a visible newline after BEGIN PGP SIGNATURE-+, and before -+END)

(collection-detail.scss already does it for pre but not for code)

[brumik]

Thank you. I was lazy here initially. I updated it to use PF components (which displaying it correctly)