Merge multiple file configs

[knightpp]

Is your feature request related to a problem? Please describe.

I use treefmt.withConfig from nixpkgs and it generates a wrapper like treefmt --config-file /nix/store/vykk3qvdjrnmvgp4pmw4jy2kdb8321fm-treefmt.toml.

Describe the solution you'd like

I'd like to have the wrapper but also configure exclusions per project. I think treefmt.toml in root dir should be merged with other configs into the global config.

Describe alternatives you've considered

I've tried setting exclusions in treefmt.toml but it didn't work.

excludes = ["assets/temml.min.js"]

Though, TREEFMT_EXCLUDES env var worked.

Additional context