Judging from `"${pkgs.element-web}/config.sample.json"`,
this needs be a URL starting with `https://`; without it one gets:
Your Element is misconfigured
Invalid base_url for m.homeserver
* Linkify all service options used in the code-examples.
* Demonstrated the use of `riot-web.override {}`.
* Moved the example how to configure a postgresql-database for
`matrix-synapse` to this document from the 20.03 release-notes.
