Examine source code of BBB-Volume

{
  "name": "BBB-Volume",
  "version": "1.0",
  "description": "Change the volume of your BBB-Session by Mb175",
  "manifest_version": 2,
  "icons": {
    "16": "icons/16.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/html5client/join?sessionToken*"
      ],
      "js": [
        "content-script.js"
      ]
    }
  ]
}