Добавил cache.manifest

build/webpack.prod.config.js

@@ -9,6 +9,7 @@ const MiniCssExtractPlugin = require('mini-css-extract-plugin');
 const CleanWebpackPlugin = require('clean-webpack-plugin');
 const HtmlWebpackPlugin = require('html-webpack-plugin');
 const CopyWebpackPlugin = require('copy-webpack-plugin');
+const AppCachePlugin = require('appcache-webpack-plugin');
 
 const publicDir = path.resolve(__dirname, '../dist/tmp/public');
 const clientDir = path.resolve(__dirname, '../client');
@@ -53,6 +54,7 @@ module.exports = merge(baseWpConfig, {
             template: `${clientDir}/index.html.template`,
             filename: `${publicDir}/index.html`
         }),
-        new CopyWebpackPlugin([{from: `${clientDir}/assets/*`, to: `${publicDir}/`, flatten: true}])
+        new CopyWebpackPlugin([{from: `${clientDir}/assets/*`, to: `${publicDir}/`, flatten: true}]),
+        new AppCachePlugin({})
     ]
 });