Tag chunk load error with ChunkLoadError

[jorrit]

The Webpack runtime sets the name of chunk load errors to ChunkLoadError (see for example https://github.com/webpack/webpack/blob/1f13ff9fe587e094df59d660b4611b1bd19aed4c/lib/css/CssLoadingRuntimeModule.js#L350).

My suggestion is to also add this to the error thrown by mini-css-extract-plugin (around https://github.com/webpack-contrib/mini-css-extract-plugin/blob/d5e540baf8280442e523530ebbbe31c57a4c4336/src/index.js#L877).

[jorrit]

Thanks!