Authentication type for anonymous access

[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-relation-for-anonymous-access

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The https://librarysimplified.org/rel/auth/anonymous link relation can be used as a value in the type array to indicate that it's okay to get books from this site without providing any authentication.

If https://librarysimplified.org/rel/auth/anonymous shares the type array with another authentication mechanism, it means that it's also possible to authenticate with the site, possibly getting access to additional books or features.

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