npm install --save-dev file-extract-loader

webpack.config.js

var cssPath="css-path";
var cssExtract = new ExtractTextPlugin(cssPath+'/[name].css');

module.exports = {
  module: {
    rules: [
      {
        test: /\.(png|jpg|gif)$/,
        use: [
          {
            loader: 'file-extract-loader',
            options: {
		name: '[name].[ext]?[hash]',
		relativePath:cssPath	
	    }  
          }
        ]
      }
    ]
  }
}