fix: regression with options.plugins {Function} (webpack.config.js) (#229)

Author: evilebottnawi

lib/options.js

@@ -1,14 +1,14 @@
 'use strict'
 
 module.exports = function parseOptions (params) {
-  if (typeof params === 'function') {
-    params = params.call(this, this)
+  if (typeof params.plugins === 'function') {
+    params.plugins = params.plugins.call(this, this)
   }
 
   let plugins
 
-  if (typeof params === 'undefined') plugins = []
-  else if (Array.isArray(params)) plugins = params
+  if (typeof params.plugins === 'undefined') plugins = []
+  else if (Array.isArray(params.plugins)) plugins = params.plugins
   else plugins = params.plugins
 
   const options = {}