Add and configure eslint

.eslintrc.cjs

@@ -0,0 +1,19 @@
+module.exports = {
+  env: {
+    browser: true,
+    es2021: true,
+    node: true,
+  },
+  extends: ['airbnb-base', 'prettier'],
+  overrides: [],
+  parserOptions: {
+    ecmaVersion: 'latest',
+    sourceType: 'module',
+  },
+  rules: {
+    'import/extensions': [2, 'always'],
+    'no-plusplus': ['error', { allowForLoopAfterthoughts: true }],
+    'no-param-reassign': ['error', { props: false }],
+    'no-bitwise': ['error', { allow: ['<<', '&'] }],
+  },
+};

package.json

@@ -13,6 +13,10 @@
   "license": "MIT",
   "devDependencies": {
     "@vitest/coverage-c8": "^0.31.0",
+    "eslint": "^8.41.0",
+    "eslint-config-airbnb-base": "^15.0.0",
+    "eslint-config-prettier": "^8.8.0",
+    "eslint-plugin-import": "^2.27.5",
     "vitest": "^0.31.0"
   }
 }