Rewrite .eslintrc.tests_newsletter_editor.js to new config format

[MAILPOET-5015]

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

@@ -0,0 +1,40 @@
+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,
+    },
+  },
+];