Examine source code of Jira Timer

{
  "manifest_version": 2,
  "name": "Jira Timer",
  "version": "1.0.5resigned1",
  "description": "Adds timer for comfortable jira work logging.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "*://support.tais.ru/browse/*",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://support.tais.ru/*"
      ],
      "js": [
        "js/jquery-3.2.1.min.js",
        "js/timer.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{473cd504-8df4-414e-8825-6c316660d0d6}"
    }
  }
}