Add an example for config.toml in the repository root

What feature would you like to see?

Proposal

Add a config.toml.example file to clarify which configuration options are available and the required order in which they must appear.

What problem will this solve?

This will help answer the questions: Which configuration keys are available? and How and where should they be set?

Relevant issues:

The preferred_auth_method is mentioned in README but it's not present in config.md.

"Recall that in TOML, root keys must be listed before tables."

^This comment is under the model_providers section in config.md, pretty easy to miss when reading other sections of the doc directly. For instance:
notify in config.md doesn't indicate that adding it at the bottom will not work and will practically fail silently because of the mismatch in order of declaration of root keys.

While this might be a common knowledge to some, it's better to provide an example, will also be handy to streamline nested configs in the future.

Are you interested in implementing this feature?

Yes! I'd love pick it up.

Additional information

Some examples of repos doing this:

• https://gitlab.com/gitlab-org/gitlab-runner/-/blob/main/config.toml.example
• https://github.com/rust-lang/rust/blob/master/bootstrap.example.toml