Fix TypeError post Stylelint update
Fix TypeError post Stylelint update

`postcss-scss` expects `postcss@8`, this therefore caused the error `TypeError: Class extends value undefined is not a constructor or null` when running Stylelint

see: https://github.com/stylelint-scss/stylelint-config-standard-scss/issues/5#issuecomment-961709882

ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments,ministryofjustice/advocate-defence-payments