Examine source code of Send to PocketBook

{
  "manifest_version": 3,
  "version": "1.0",
  "name": "Send to PocketBook",
  "description": "Save documents in your PocketBook while browsing, by using the Send-To-PocketBook functionality.",
  "icons": {
    "16": "icons/icon_16.png",
    "48": "icons/icon_48.png"
  },
  "action": {
    "default_popup": "action/default_popup.html"
  },
  "permissions": [
    "scripting",
    "activeTab",
    "storage"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "web_accessible_resources/*",
        "/*.json",
        "/*.js",
        "/*.css"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "content_security_policy": {
    "extension_pages": "script-src 'self'; object-src 'self'; "
  },
  "background": {
    "scripts": [
      "background/service_worker.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "send-to-pocketbook@extension-js"
    }
  }
}