Add ESLint config and Node.js test suite (198/198 passing)

eslint.config.js

@@ -0,0 +1,23 @@
+import js from '@eslint/js';
+import globals from 'globals';
+
+export default [
+  js.configs.recommended,
+  {
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        ...globals.node,
+      },
+      ecmaVersion: 2022,
+      sourceType: 'module',
+    },
+    rules: {
+      'no-var': 'error',
+      'no-unused-vars': ['warn', { args: 'none' }],
+      'semi': ['error', 'always'],
+      'no-console': 'off',
+      'no-constant-condition': 'off',
+    },
+  },
+];