Make sure that vendors chunk from CRA2 is preloaded first

[stereobooster]

Follow up for #252

[raRaRa]

Is this still an issue? I tried using react-snap on my CRA2, but when I view the generated files in my browser I get a lot of warnings like:
The resource http://localhost:8000/static/js/5.f6bab7d8.chunk.js was preloaded using link preload but not used within a few seconds from the window's load event. Please make sure it has an appropriate as value and it is preloaded intentionally.