Examine source code of Two Factor Authenticator

{
  "manifest_version": 2,
  "name": "Two Factor Authenticator",
  "version": "1.3.3resigned1",
  "description": "Generates TOTPs for 2 factor authentication",
  "applications": {
    "gecko": {
      "id": "authenticator@r01"
    }
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "storage"
  ],
  "background": {
    "scripts": [
      "webext_utilities.js",
      "authenticator-bg.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "browser_action": {
    "browser_style": true,
    "default_popup": "browserAction.html",
    "default_icon": "icons/icon.svg"
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Alt+Shift+A"
      }
    }
  }
}