Insert banner to let the user know a document is available for free in the Download confirmation page in Appellate Pacer

[ERosendo]

The extension should insert a banner on the download page to notify the user that a document is available for free in the RECAP archive. Here's a screenshot of the page from Appellate Pacer:

Here's a screenshot for reference from the district PACER:

We can visit the download page following this link: Download page