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: ['<<', '&'] }],
+  },
+};