Examine source code of Custom CSS Injector v2

{
  "manifest_version": 2,
  "name": "Custom CSS Injector",
  "version": "1.0",
  "description": "Apply custom CSS styles to the current webpage.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/css-48.png",
    "default_popup": "popup.html",
    "default_title": "Custom CSS Injector"
  },
  "icons": {
    "48": "icons/css-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{75969426-be5b-45a6-a7a3-19f0b98b2bc2}"
    }
  }
}