Enable purgeCSS in webpack

webpack.config.js

const purgecss = require('@fullhuman/postcss-purgecss')({
  // Specify the paths to all of the template files in your project
  content: [
    './src/**/*.html',
    './src/**/*.js',
  ],
  // Used to extract class names from your templates
  defaultExtractor: content => {
    // Capture as liberally as possible
    const broadMatches = content.match(/[^<>"'`\s]*[^<>"'`\s:]/g) || []
    // Capture classes within other delimiters
    const innerMatches = content.match(/[^<>"'`\s.()]*[^<>"'`\s.():]/g) || []
    return broadMatches.concat(innerMatches)
  }
})