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

.eslintignore

@@ -0,0 +1,8 @@
+# dependencies:
+node_modules/
+
+# build output:
+dist/
+
+# test coverage output:
+coverage/

.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"
+  }
+};

package.json

@@ -1,2 +1,11 @@
-.eslintrc.js
-.eslintignore
+{
+  "name": "my-project",
+  "version": "1.0.0",
+  "private": true,
+  "scripts": {
+    "lint": "eslint ."
+  },
+  "devDependencies": {
+    "eslint": "^8.0.0"
+  }
+}