Merge newsletter tests config into ES5 config

[MAILPOET-5015]

packages/js/eslint-config/eslint-es5.config.js

@@ -3,6 +3,7 @@ const FlatCompat = require('@eslint/eslintrc').FlatCompat;
 const airbnbLegacyConfig = require('eslint-config-airbnb/legacy');
 const prettierConfig = require('eslint-config-prettier');
 const importPlugin = require('eslint-plugin-import');
+const noOnlyTestsPlugin = require('eslint-plugin-no-only-tests');
 const globals = require('globals');
 
 // compat configs
@@ -26,11 +27,13 @@ module.exports = [
     },
     plugins: {
       import: importPlugin,
+      'no-only-tests': noOnlyTestsPlugin,
     },
     rules: {
       'import/prefer-default-export': 0, // we want to stop using default exports and start using named exports
       'no-underscore-dangle': 0, // Backbone uses underscores, we cannot remove them
       'import/no-default-export': 1, // no default exports
+      'no-only-tests/no-only-tests': 2,
     },
   },
 ];

packages/js/eslint-config/eslint-tests-newsletter-editor.config.js

@@ -1,40 +0,0 @@
-const babelParser = require('@babel/eslint-parser');
-const FlatCompat = require('@eslint/eslintrc').FlatCompat;
-const airbnbLegacyConfig = require('eslint-config-airbnb/legacy');
-const prettierConfig = require('eslint-config-prettier');
-const importPlugin = require('eslint-plugin-import');
-const noOnlyTestsPlugin = require('eslint-plugin-no-only-tests');
-const globals = require('globals');
-
-// compat configs
-const compat = new FlatCompat({ baseDirectory: __dirname });
-const airbnbLegacyCompatConfig = compat.config(airbnbLegacyConfig);
-const prettierCompatConfig = compat.config(prettierConfig);
-
-module.exports = [
-  ...airbnbLegacyCompatConfig,
-  ...prettierCompatConfig,
-  {
-    languageOptions: {
-      parser: babelParser,
-      parserOptions: {
-        ecmaVersion: 6,
-        sourceType: 'module',
-      },
-      globals: {
-        ...globals.mocha,
-      },
-    },
-    plugins: {
-      import: importPlugin,
-      'no-only-tests': noOnlyTestsPlugin,
-    },
-    rules: {
-      'no-only-tests/no-only-tests': 2,
-      // Exceptions
-      'func-names': 0,
-      // Temporary
-      'no-underscore-dangle': 0,
-    },
-  },
-];