Examine source code of Kenteken, pls

{
  "manifest_version": 2,
  "name": "Kenteken, pls",
  "description": "Gemakkelijk testen met kentekens, kies een categorie en kenteken, pls zal een willekeurig (actief) kenteken invoegen in het veld.",
  "version": "1.3.3",
  "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self';",
  "permissions": [
    "contextMenus",
    "activeTab",
    "scripting",
    "*://opendata.rdw.nl/resource/m9d7-ebf2.json"
  ],
  "commands": {
    "kenteken-pls": {
      "suggested_key": {
        "default": "Alt+Shift+K",
        "mac": "Command+Shift+K"
      },
      "description": "Kenteken invoegen"
    }
  },
  "icons": {
    "16": "16.750bd5c2.png",
    "48": "48.3b64bdbe.png",
    "128": "128.c9a8f1aa.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "app.0a4bf782.js"
      ],
      "css": []
    }
  ],
  "background": {
    "scripts": [
      "background.9915c459.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e5c67285-1ea7-4367-8157-7203f3b60776}"
    }
  }
}