Examine source code of The Owl Twitter

{
  "manifest_version": 2,
  "description": "Customize your twitter with The Owl House theme",
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "96": "icons/icon-96.png"
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage"
  ],
  "name": "The Owl Twitter",
  "version": "1.0",
  "content_scripts": [
    {
      "js": [
        "script.js"
      ],
      "matches": [
        "https://twitter.com/*"
      ],
      "run_at": "document_idle"
    }
  ],
  "web_accessible_resources": [
    "images/*.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{d4588d96-ab9e-471b-b220-8c039811ef8b}"
    }
  }
}