Link from root OPDS feed

[leonardr]

This is one of a series of proposals for taking NYPL's extensions to Authentication For OPDS and adding them to the core document.

https://github.com/NYPL-Simplified/Simplified/wiki/Authentication-For-OPDS-Extensions#link-to-the-a4opds-document-from-server-root

The root feed of an OPDS server should link to its Authentication For OPDS document using rel="http://opds-spec.org/auth/document" and a type that makes it clear the document on the other end is an A4OPDS document (that is, type="application/vnd.opds.authentication.v1.0+json"). This guarantees that a client can always find the A4OPDS document. If the root feed requires authentication, that's fine, because the A4OPDS document is also supposed to be served as the entity-body of a 401 response.

This makes it easy to find the A4OPDS document without stumbling around the catalog hoping to trigger a 401.