Examine source code of Watermark Pages

{
  "manifest_version": 3,
  "name": "Watermark Pages",
  "description": "Inject a watermark into pages while browsing.",
  "version": "1.1.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "{25c3b2ba-157f-4669-ab94-6c4edd6b2814}"
    }
  },
  "action": {
    "default_popup": "index.html",
    "default_icon": "favicon-32x32.png"
  },
  "icons": {
    "32": "favicon-32x32.png",
    "512": "android-chrome-512x512.png"
  },
  "host_permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "run_at": "document_idle",
      "js": [
        "watermark.js"
      ],
      "css": [
        "watermark.css"
      ]
    }
  ]
}