Examine source code of Meeting Timer

{
  "name": "Meeting Timer",
  "description": "Display a Timer on Google Meet calls based on your Google Calendar events. Get a quick access to Google Calendar.",
  "version": "3.1.9",
  "manifest_version": 2,
  "icons": {
    "16": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Meeting Timer",
    "default_icon": "icon.png"
  },
  "permissions": [
    "identity",
    "identity.email",
    "storage",
    "tabs",
    "alarms",
    "idle",
    "<all_urls>"
  ],
  "options_page": "options.html",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScriptAll.js"
      ]
    },
    {
      "matches": [
        "https://meet.google.com/*",
        "https://app.zoom.us/wc/*",
        "https://teams.live.com/_#/modern-calling/*"
      ],
      "js": [
        "contentScriptMeeting.js"
      ]
    }
  ],
  "key": "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAhIirQV82YNUHlpd6nrAfKlm1JF4/frIMtn20nzh3RrN3WEDj5g1k4KDv9k6lidJ027YCGM5bpVhrCNLObASzCyYBey+kqGmL+P+i58teOQnntk+brARPK6u7tKURO/wEZWEXCMpjDzi0vmbc9s16ZYGyUqbDRq4FvKGgPs75xz1rtj4DSwvXj0ljXHyWpsnZjvZX1NmOvkQzhP0oIKTy4sFFFB0xn1GcEwqjsx+e0V8LwkW/N1rfGuBNmAzTmxqDeVxmT/ZZxfQSsxntykCr+JrdewTyBvy5SSbwDymdQKRm3h0yuaKAB3n3lD9yOH13cYavmxkepCQx72qkfv1+JwIDAQAB",
  "oauth2": {
    "client_id": "1002779629404-h9pat74pba8n31nufga2m1ol610ugaa5.apps.googleusercontent.com",
    "scopes": [
      "https://www.googleapis.com/auth/calendar.readonly",
      "https://www.googleapis.com/auth/calendar.events"
    ]
  },
  "web_accessible_resources": [
    "*.mp3",
    "*.ttf",
    "*.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{d89e072c-f355-4ac9-8eae-a16f8fd94415}"
    }
  }
}