Examine source code of Reduced Subtitles

{
  "manifest_version": 2,
  "name": "Reduced Subtitles",
  "version": "1.0",
  "description": "Smaller and transparent subtitles for ITVX",
  "icons": {
    "48": "cat.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "cat.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://itv.com/*",
        "https://www.itv.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ffafbe46-3104-4b3d-9af3-588f2665e61a}"
    }
  }
}