Supported values are,
- `none` for no author information,
- `full` for both the name and email,
- `name` for just the name,
- `username` for username part of the email,
- (default) `email` (or any other gibberish for that matter) for the full email.
Can be used with tools like taplo-lsp to show hints & validation in
editors/IDEs. Won't apply automatically to config files until it's
submitted to schemastore.org, but in the meantime it can be used via a
schema directive
(https://taplo.tamasfe.dev/configuration/directives.html#the-schema-directive)
or other manual config mechanism.
Context in #879.
