Examine source code of BlueCheck

{
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*",
        "https://www.twitter.com/*",
        "https://mobile.twitter.com/*"
      ],
      "js": [
        "twitter.js"
      ],
      "run_at": "document_end",
      "all_frames": false
    }
  ],
  "description": "Replace Twitter Verification from Blue accounts",
  "developer": {
    "name": "armelin1"
  },
  "icons": {
    "128": "icon128.png"
  },
  "manifest_version": 2,
  "name": "BlueCheck",
  "permissions": [
    "*://twitter.com/*",
    "*://*.twitter.com/*"
  ],
  "version": "1.0.3",
  "browser_specific_settings": {
    "gecko": {
      "id": "{7e2d8f28-9c10-4806-a8de-04cc283bbe3e}"
    }
  }
}