Examine source code of Twitter Volume Control

{
  "name": "Twitter Volume Control",
  "version": "1.3.2resigned1",
  "description": "Adds a volume slider to twitter videos - TWITTER HAS A NATIVE ONE NOW",
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/i/videos/*"
      ],
      "js": [
        "script.js"
      ],
      "all_frames": true
    }
  ],
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{e2a09856-7cfb-4003-a666-9cc7bf30125a}"
    }
  }
}