Examine source code of MessengerTutis

{
  "name": "MessengerTutis",
  "version": "1.4",
  "description": "Geresnės reakcijos jūsų Messenger!",
  "manifest_version": 2,
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "webRequest",
    "https://*.xx.fbcdn.net/images/emoji.php/*",
    "https://www.messenger.com/*",
    "https://www.facebook.com/*",
    "webRequestBlocking",
    "activeTab"
  ],
  "web_accessible_resources": [
    "*.png"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.messenger.com/*",
        "https://www.facebook.com/*"
      ],
      "css": [
        "messenger.css"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}