feat: use .editorconfig values as fallback config source

[twelvelabs]

I already have things like indent size configured in .editorconfig. I'd love to have jsonfmt use those settings.

Would you be open to a PR that includes editorconfig-core-go and uses .editorconfig values as defaults?

Similar issue: https://github.com/google/yamlfmt/issues/61

[caarlos0]

hey, missed this issue somehow... yeah, that would be great!