Chore: Upgrade website to use Hugo to v0.157 or later

[stumbo]

Hugo versions 0.156.0 and 0.157.0 have recently been released.

Hugo version 0.156.0 introduces some breaking changes. The only one that appears to effect us is the value Site.Author is deprecated and needs to be replaced. We can do this by adding a new params value, Site.params.author and making modifications to the rss.html template.

Author:
  name: "The Medley Interlisp Project"
  email: "info@interlisp.org"

This change should be timed to coincide with the next upgrade to Docsy - or, at least when Docsy upgrades and makes v0.157 their Hugo baseline.