Improve typescript example (#307)

cypress-io/cypress#2316

Author: adam187

examples/preprocessors__typescript-webpack/webpack.config.js

@@ -9,6 +9,9 @@ module.exports = {
         exclude: [/node_modules/],
         use: [{
           loader: 'ts-loader',
+          options: {
+            transpileOnly: true,
+          },
         }],
       },
     ],