Unable to format using stylelint rules with severities

[iblack10]

I've been using different severities for rules as per the stylelint docs: https://github.com/stylelint/stylelint/blob/d2166dfbcdefefacafd27afd5993ec8341c3b45e/docs/user-guide/configuration.md#severities-error--warning but it seems these are not compatible with stylefmt just now:

"indentation": [4, { "severity": "error" }]

That doesn't work - but this does:

"indentation": 4