feat(index) make mangle option configurable (#4)

Author: dweber019

src/index.ts

@@ -8,7 +8,7 @@ import * as webpack from 'webpack'
  *
  * See: https://webpack.github.io/docs/list-of-plugins.html#uglifyjsplugin
  */
-export = function uglify({debug = false, exclude = []} = {}) {
+export = function uglify({debug = false, exclude = [], mangle = {screw_ie8 : true, keep_fnames: true}} = {}) {
   return function uglify(this: WebpackConfig): WebpackConfig {
     const options = debug ? {
       beautify: true, //debug
@@ -27,10 +27,7 @@ export = function uglify({debug = false, exclude = []} = {}) {
     } : {
       beautify: false, //prod
 
-      mangle: {
-        screw_ie8 : true,
-        keep_fnames: true
-      }, //prod
+      mangle: mangle, //prod
 
       exclude: exclude,