fix: shadowMode still has to be an option

Author: yyx990803

lib/index.js

@@ -38,7 +38,7 @@ module.exports = function (source) {
   const options = loaderUtils.getOptions(loaderContext) || {}
 
   const isServer = target === 'node'
-  const isShadow = incomingQuery.shadow != null
+  const isShadow = !!options.shadowMode
   const isProduction = options.productionMode || minimize || process.env.NODE_ENV === 'production'
   const filename = path.basename(resourcePath)
   const context = rootContext || process.cwd()