Examine source code of Twitter Customizer

{
  "manifest_version": 2,
  "name": "Twitter Customizer",
  "version": "1.0",
  "description": "Enhance your Twitter experience with custom color schemes.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "https://twitter.com/*"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{decc638b-f92d-402a-ab49-c2bef04cbd0a}"
    }
  }
}