Examine source code of Kasowacz Reklam

{
  "manifest_version": 2,
  "name": "Kasowacz Reklam",
  "version": "1.3",
  "description": "Będzie kasować reklamy na poczcie",
  "icons": {
    "48": "icons/border-48.png"
  },
  "applications": {
    "gecko": {
      "id": "{a6e84df4-63eb-4f5f-8a70-0d8b45da8739}",
      "strict_min_version": "42.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://poczta.interia.pl/*"
      ],
      "js": [
        "deleter.js"
      ]
    }
  ]
}