Gatsby: Consider using Critters for inlining critical CSS

[kripod]

Summary

Recently, a webpack plugin has been released by GoogleChromeLabs to inline critical CSS without the overhead of using a headless browser.

Motivation

Gatsby is all about performance. I think that the project could benefit a lot from squeezing every bits of performance optimizations available.

[KyleAMathews]

Due to the high volume of issues, we're closing out older ones without recent activity. Please open a new issue if you need help!

[KyleAMathews]

Also, this would be a sweet plugin if someone wants to write it and publish it to npm.

[DylanTackoor]

@KyleAMathews I'ma try making one

[KyleAMathews]

@DylanTackoor awesome!