Examine source code of Talky volume

{
  "manifest_version": 2,
  "name": "talky-volume",
  "version": "1.0",
  "content_scripts": [
    {
      "matches": [
        "https://talky.io/*"
      ],
      "js": [
        "talky-volume.js"
      ],
      "css": [
        "style.css"
      ]
    }
  ]
}