package.json: add support for auto-fixing lint errors

Simply run `npm run lint:fix`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

package.json

@@ -6,6 +6,7 @@
   },
   "scripts": {
     "lint": "eslint -c eslint.config.js '**/*.js'",
+    "lint:fix": "eslint --fix -c eslint.config.js '**/*.js'",
     "test": "jest"
   }
 }