message: fix(webpack): put back  custom css variable flag
diff: @@ -70,6 +70,7 @@ const styleLoaders = [
  data: `
  $feature-flags: (
  ui-shell: true,
  + enable-css-custom-properties: true
  );
  $dds-feature-flags: (
  carbon-expressive: ${useCarbonExpressive},
  