Use development mode in webpack in scaffolded projects

Author: alandipert

inst/templates/widget_webpack.config.js.txt

@@ -1,6 +1,7 @@
 var path = require('path');
 
 module.exports = {
+    mode: 'development',
     entry: path.join(__dirname, 'srcjs', '${name}.js'),
     output: {
         path: path.join(__dirname, 'inst', 'htmlwidgets'),