Examine source code of meet-default-mic

{
  "manifest_version": 2,
  "name": "meet-default-mic",
  "version": "1.4.0",
  "description": "Automatically choose the user's preferred microphone in Google Meet",
  "homepage_url": "https://github.com/sjahu/meet-default-mic",
  "browser_specific_settings": {
    "gecko": {
      "id": "meetdefaultmic@shumphries.ca"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://meet.google.com/*-*-*"
      ],
      "js": [
        "meet-default-mic.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "permissions": [
    "storage"
  ]
}