Find a better config documentation solution than json schema

[markmandel]

Is your feature request related to a problem? Please describe. People in Discord find the json schema documentation confusing. Particularly https://googleforgames.github.io/quilkin/main/book/proxy-configuration.html - they think the schema is an example, not a schema.

Describe the solution you'd like

Several options, of which we could do all/some of:

1. Make sure we always point to the Rust configuration options (which we do almost everywhere for FIlters, but not for the main config), for those that are more familiar looking at RustDoc. (although Quilkin config rustdoc has several non-public items).
2. Use an automation tool to take the schema configuration (such as https://github.com/adobe/jsonschema2md), and use that as part of our documentation generation.
3. Retain the schema as well, for those that wish to see it.

This is also related to / possibly dependent on #579.

Describe alternatives you've considered

Leave things as is, but I think we could do better with our documentation here.

Additional context

https://discord.com/channels/773975408265134100/773975408856399894/1034241596373352500