Examine source code of easyStempel

{
  "manifest_version": 2,
  "name": "easyStempel",
  "description": "Fügt Einstempeln/Ausstempeln Buttons zu personio hinzu",
  "version": "0.0.2",
  "icons": {
    "64": "icons/icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.personio.de/*"
      ],
      "js": [
        "content_script.js"
      ],
      "css": [
        "content_script.css"
      ]
    }
  ],
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{360156e0-7bd9-4fd8-8164-99ae087e52ac}"
    }
  }
}