Imho the best configuration file is code written in the language itself.

Configuring TypeScript applications with the `defineConfig` pattern that takes asynchronous callbacks allowing you to code over settings is very useful. And it's fully typed and programmable.

It's particularly useful because it also allows you to trivially use one single configuration file where you only set what's different between environments with some env === "local" then use this db dependency or turn on/off sentry, etc.

Zig is another language that shows that configuration and building should just be code in the language itself.