postcss overwrite use mode:'file' will cause crash

[Landon-CN]

craco: 6.4.3
react-scripts: 5.0.0

craco.config.js

style: {
    postcss: {
      mode: 'file',
      loaderOptions: {
        config: {
          path: path.resolve(__dirname, './postcss.config.js'),
        },
      },
    },
  }

error:

why:
https://github.com/gsoft-inc/craco/blob/master/packages/craco/lib/features/webpack/style/postcss.js#L29

craco read match.loader.options.ident
but react-scripts move ident to postcssOptions
https://github.com/facebook/create-react-app/blob/v5.0.0/packages/react-scripts/config/webpack.config.js#L139

it create less plugin crash

[patricklafrance]

Duplicate of #378