upgraded all npm packages (webpack 5, eslint 7, etc) and activated eslint

build/webpack.config.prod.js

@@ -1,7 +1,7 @@
 'use strict'
 
 const webpack = require('webpack')
-const merge = require('webpack-merge')
+const { merge } = require('webpack-merge')
 const baseConfig = require('./webpack.config.base')
 const MiniCssExtractPlugin  = require('mini-css-extract-plugin')
 const TerserPlugin = require("terser-webpack-plugin");
@@ -40,18 +40,26 @@ module.exports = merge(baseConfig, {
     minimize: true,
     minimizer: [
       new TerserPlugin({
-        sourceMap: true, // Must be set to true if using source-maps in production
         parallel: true,
         test: /\.(js|vue)$/,
         // extractComments: true
         terserOptions: {
           compress: {
-            drop_console: true,
+            // drop_console: true,
+            pure_funcs: [
+                'console.log',
+                'console.info',
+                'console.debug'
+                // 'console.warn'
+            ]
           },
         },
       })
     ],
   },
-  // ,
-  // plugins: []
+  plugins: [
+    new webpack.DefinePlugin({
+      'process.env.NODE_ENV': JSON.stringify('production')
+    })
+  ]
 })