Consult the default resource related to an item when it is a PDF

[benel]

While it could be done by clicking on a link (see #331, the experience would be better if it was displayed (as images are) directly on the item page.

Possible usable package: https://www.npmjs.com/package/react-pdf

This would require to determine its MIME type first. Please note that due to cross origin limitations, it is not possible with external resources. But it could be done on attached files (#142).

Phase 1

• [ ] Scenarios (Gherkin)
• [ ] Mockups
• [ ] Implementation strategy

Phase 2

• [ ] Acceptance tests (Capybara)
• [ ] Implementation

Phase 3

• [ ] Screencast