Render the page takes a long time

[petersolopov]

Hi there! Thanks for the great plugin!

I have performance issue. My screenshots tests take a very long time. I started digging it and I found out the reason. The plugin has middleware that renders HTML pages for test. It has a call webpackStats.toJson() that takes in my case around 1s.

We need only assetsByChunkName information in stats for render html. webpackStats.toJson(options) provide passing settings: docs. With this paramswebpackStats.toJson({ chunk: false, modules: false }) the call takes no time.

I've created PR with this changes