Adding eslint.

package.json

@@ -17,6 +17,11 @@
   ],
   "devDependencies": {
     "@purtuga/esm-webpack-plugin": "^1.1.1",
+    "eslint": "^7.20.0",
+    "eslint-config-standard": "^16.0.2",
+    "eslint-plugin-import": "^2.22.1",
+    "eslint-plugin-node": "^11.1.0",
+    "eslint-plugin-promise": "^4.3.1",
     "webpack": "^4.41.2",
     "webpack-cli": "^3.3.10"
   },
@@ -31,7 +36,8 @@
   "library": "./main.js",
   "scripts": {
     "prepare": "npm run build",
-    "build": "webpack --mode=production"
+    "build": "webpack --mode=production",
+    "lint": "npx eslint --ext .js ."
   },
   "staticDirs": {},
   "translations": {