Examine source code of OpenCheck for Twitter

{
  "manifest_version": 2,
  "name": "OpenCheck",
  "version": "1.0.0",
  "description": "Displays OpenCheck identity verification on profiles and timeslines on twitter.com",
  "permissions": [
    "*://api.opencheck.is/*",
    "webRequest"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*"
      ],
      "js": [
        "opencheck.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "192": "icons/opencheck-192.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ee497b05-23cf-4fbf-822f-f1ced832b5a0}"
    }
  }
}