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

.eslintrc.js

@@ -0,0 +1,38 @@
+module.exports = {
+  parserOptions: {
+    parser: 'babel-eslint'
+  },
+  extends: [
+    'eslint:recommended',
+    'plugin:vue/vue3-recommended',
+    'plugin:vue-a11y/base',
+    'standard',
+    // 'plugin:prettier/recommended'
+  ],
+  plugins: [
+    'vue',
+    'vue-a11y'
+  ],
+  rules: {
+    'no-unused-vars': ["warn"],
+  },
+  ignorePatterns: [
+    "vendor/**",
+    "web/core/**"
+  ],
+  globals: {
+    "Drupal": true,
+    "drupalSettings": true,
+    "drupalTranslations": true,
+    "domready": true,
+    "jQuery": true,
+    "_": true,
+    "matchMedia": true,
+    "Cookies": true,
+    "Backbone": true,
+    "Modernizr": true,
+    "Popper": true,
+    "Sortable": true,
+    "CKEDITOR": true
+  }
+}