Examine source code of GChat ThreadLink

{
  "manifest_version": 2,
  "name": "GChat ThreadLink",
  "version": "1.0",
  "description": "Adds a permalink to all chat threads.",
  "browser_specific_settings": {
    "gecko": {
      "id": "gchat_permalink@example.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://chat.google.com/*"
      ],
      "js": [
        "thread-link.js"
      ]
    }
  ]
}