Atom feed does not validate

The W3C validator complains about several parts of the Atom feed (links without hrefs, etc.) The invalid feed causes some services, like IFTTT, to not be able to work with it.

Cf. https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fjobs.code4lib.org%2Fjobs.atom