Examine source code of Telegram Username Checker

{
  "manifest_version": 2,
  "name": "Telegram Username Checker",
  "version": "1.0",
  "description": "Telegram Username Checker is a cool extension. This extension allows users to check if a username is available on Telegram or not.",
  "permissions": [],
  "browser_action": {
    "default_popup": "game.html",
    "default_icon": {
      "128": "images/tele-logo.png"
    }
  },
  "icons": {
    "128": "images/tele-logo.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{74300520-073d-4fac-b444-a6b57f0f07cc}"
    }
  }
}