Examine source code of VimeoSubtitleDownloader

{
  "manifest_version": 2,
  "name": "Network VTT File Downloader",
  "version": "1.1",
  "description": "Detect and download VTT files from the Network tab.",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "permissions": [
    "activeTab",
    "webRequest",
    "webRequestBlocking",
    "downloads",
    "*://*/*"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d40bee72-9f74-476a-ab0c-26949faacb11}"
    }
  }
}