Show spinner until preview is present

[kirahowe]

When a new resource is created the preview doesn't always come fast enough and sometimes the user sees only the link on the homepage. Add a spinner to these links and poll to see if the resource.preview is present (and expected to come, i.e. a job was queued for it), if it is, re-render the resource card to show all the data. If it's not, keep showing the spinner.

• add tracking for job creation (have to know if a job was created for this preview fetch)
• if it was, show a spinner on the index until the preview is present
• if it wasn't, show a friendly message like "We couldn't seem to fetch any data about this resource. Can you add a descriptive title and short description?"