Examine source code of ReadShape Kindle Sync

{
  "manifest_version": 3,
  "name": "ReadShape Kindle Sync",
  "short_name": "rks",
  "icons": {
    "32": "logo32.png",
    "64": "logo64.png",
    "192": "logo192.png",
    "512": "logo512.png"
  },
  "version": "1.1.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "kindle-sync-extension@readshape.com",
      "strict_min_version": "109.0"
    }
  },
  "description": "Extension for syncing Amazon Cloud highlights with ReadShape.",
  "permissions": [
    "cookies",
    "storage"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "index.html"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*/*",
        "http://*/*"
      ],
      "js": [
        "browser-polyfill.js"
      ]
    }
  ],
  "host_permissions": [
    "*://*.readshape.com/*",
    "*://*.amazon.com/*"
  ],
  "action": {
    "default_popup": "index.html"
  }
}