How to configure whitespace (e.g. spaces, new lines)

First of all, thank you for writing this tool. It is no doubt a lot of work.

I'd like to give elm (and this formatter) another try, but the default whitespace settings (4 spaces, two lines between declarations, etc.) are a bit much for me. Based on previous issues and PRs, I know you have no interest in adding a `config` option. But is there a file or two that hold all the rules, so that I could fork this repo and change what I need?

The issue does not name any files, tests, or entry points. First determine where elm-format's whitespace rules are defined and whether changing them is a supported, self-contained task; done would mean identifying those rules and documenting a viable fork-based customization path.

Written by the indexing model from the issue text.