Configuration documentation: Add a first example and name sections

[MakisH]

The configuration documentation explains the different settings, without first giving an overview. This PR adds such an overview and the exact names of the sections in the config.

Checklist:

• I made sure that the CI passed before I ask for a review.
• I added a summary of the changes (compared to the last release) in the CHANGELOG.md.
• If necessary, I made changes to the documentation and/or added new content.
• I will remember to squash-and-merge, providing a useful summary of the changes of this PR.

[IshaanDesai]

Makes sense 👍 There was once such an example configuration, but then I removed it to make the page more concise. But having it is good.

[fsimonis]

This is partially overlapping with #253