A Gatsby post-build plugin that implements Uncss.
Never worry about the size of your css framework again!
It updates your html files directly, removing any unused inline styles.

$ npm install gatsby-plugin-uncss

In your gatsby-config.js file:

module.exports = {
  plugins: [
    {
      resolve: 'gatsby-plugin-uncss'
      options: {
        uncssOptions: { /* ... */ }
      }
    }
  ]
}

Uncss options are documented here.