How to set a default custom preset for linter-jscs to use with Atom Editor?

Question

Using linter-jscs for Atom Editor, is there a way to set a default custom jscs preset for all projects?

After reading the docs, I tried editing the file .atom/packages/linter-jscs/.jscsrc with the following code but it seemed to be ignored:

{
    "preset": "./custom.json"
}

Were can I define the custom configuration file?

Thanks!

EDIT:

Ok, I understand that the "preset:" configuration should be done in config.cson. But still, I can't get to point to a json file in the same directory as config.cson