You have a problem and you need a configuration language, so you pick YAML. Now you have two problems.

Take a leaf out of Rust's book and use something simple and sane like TOML, YAML is a mess.

See: https://github.com/cblp/yaml-sucks

Otherwise this looks like a great project, please don't ruin it with YAML.

YAML sucks but so does TOML, especially when it comes to nested data structures like the layout.yaml shown on the front page.

There are no good configuration languages in existence and there never will be. We have rejected Lisp/sexp so now we must suffer endlessly.

Take a look at HOCON (Human-Optimized Config Object Notation)

https://github.com/lightbend/config/blob/main/HOCON.md

So, the project you linked to is Java / Scala: https://github.com/lightbend/config

And there're also (basic? complete?) HOCON parsers in Javascript and Rust — I investigated this a while ago, because I want to use HOCON everywhere in my projects:

https://docs.rs/hocon/0.5.1/hocon/ (Rust)

https://www.google.com/search?q=hocon+javascript (Js, a few different)

The Rust version:

> This implementation goal is to be as permissive as possible, returning a valid document with all errors wrapped in `Hocon::BadValue` when a correct value cannot be computed

How nice :- ) (it seems to me)