laipower/wp-content/themes/twentynineteen/postcss.config.js

var postcssFocusWithin = require('postcss-focus-within');

module.exports = {
    plugins: {
        autoprefixer: {}
    }
};

module.exports = {
    plugins: [
        postcssFocusWithin({
            disablePolyfillReadyClass: true
        })
    ]
};