[eslint] add eslint; rules to enable later are warnings

.eslintrc

@@ -0,0 +1,54 @@
+{
+  "root": true,
+
+  "extends": "@ljharb/eslint-config/node/0.4",
+
+  "rules": {
+    "array-bracket-spacing": 0,
+    "array-element-newline": 0,
+    "brace-style": 1,
+    "camelcase": 1,
+    "comma-dangle": 1,
+    "comma-spacing": 1,
+    "complexity": 0,
+    "curly": 1,
+    "dot-notation": 1,
+    "eol-last": 1,
+    "func-style": 1,
+    "function-paren-newline": 1,
+    "indent": [1, 4],
+    "key-spacing": 1,
+    "max-lines-per-function": 0,
+    "max-nested-callbacks": 1,
+    "max-statements": 0,
+    "multiline-comment-style": 1,
+    "no-array-constructor": 1,
+    "no-continue": 1,
+    "no-div-regex": 1,
+    "no-extra-parens": 1,
+    "no-mixed-operators": 1,
+    "no-multi-spaces": 1,
+    "no-multiple-empty-lines": 1,
+    "no-param-reassign": 1,
+    "no-plusplus": 1,
+    "no-proto": 1,
+    "no-redeclare": 1,
+    "no-restricted-syntax": 1,
+    "no-shadow": 1,
+    "no-trailing-spaces": 1,
+    "no-unused-vars": 1,
+    "no-use-before-define": 1,
+    "object-curly-newline": 1,
+    "object-curly-spacing": 1,
+    "operator-linebreak": 1,
+    "quote-props": 1,
+    "quotes": 1,
+    "semi-style": 1,
+    "semi": 1,
+    "space-before-blocks": 1,
+    "space-before-function-paren": 1,
+    "space-infix-ops": 1,
+    "strict": 1,
+    "wrap-regex": 1,
+  },
+}

package.json

@@ -4,13 +4,18 @@
     "description": "parse argument options",
     "main": "index.js",
     "devDependencies": {
+        "@ljharb/eslint-config": "^21.0.0",
         "aud": "^2.0.1",
+        "eslint": "=8.8.0",
         "nyc": "^10.3.2",
         "tape": "^5.6.1"
     },
     "scripts": {
         "prepack": "npmignore --auto --commentLines=auto",
-        "test": "nyc tape test/*.js",
+        "lint": "eslint --ext=js,mjs .",
+        "pretest": "npm run lint",
+        "tests-only": "nyc tape test/*.js",
+        "test": "npm run tests-only",
         "posttest": "aud --production"
     },
     "testling": {