Examine source code of Subtitles Seeker

{
  "manifest_version": 2,
  "name": "Subtitles Seeker",
  "icons": {
    "123": "YouTube search.svg"
  },
  "version": "1.0",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "build/background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*/*"
      ],
      "all_frames": true,
      "js": [
        "build/content-script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{0fc1c7c9-304a-42a4-b7fa-843e036ca137}"
    }
  }
}