let styles = require('./popup.css')
 ...
 this.tempContainer.innerHTML = `<h1 class=${styles.popup}> Hello world </h1>`

{        test: /\.css$/,        use: [          'style-loader',          {            loader: "css-loader",            options: {              modules: {                localIdentName: '[path][name]__[local]--[hash:base64:5]'              }            }          }        ],        include: [          path.resolve(__dirname, '/src/components')        ]      },