chore: add ESLint setup with config, ignore file, and lint script

.eslintrc.js

@@ -0,0 +1,16 @@
+module.exports = {
+  env: {
+    es2021: true,
+    node: true,
+    jest: true
+  },
+  extends: "eslint:recommended",
+  parserOptions: {
+    ecmaVersion: "latest",
+    sourceType: "module"
+  },
+  rules: {
+    // add custom rules or overrides here, e.g.:
+    // "no-console": "warn"
+  }
+};