Examine source code of Site Customizer

{
  "manifest_version": 2,
  "name": "Site Customizer",
  "version": "1.0.1",
  "description": "An extension that lets you easily customize the CSS of a website.",
  "browser_action": {
    "default_title": "Site Customizer\nCustomize this site?",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "logo/logo16.png",
      "32": "logo/logo32.png",
      "48": "logo/logo48.png",
      "64": "logo/logo64.png",
      "128": "logo/logo128.png"
    }
  },
  "icons": {
    "16": "logo/logo16.png",
    "32": "logo/logo32.png",
    "48": "logo/logo48.png",
    "64": "logo/logo64.png",
    "128": "logo/logo128.png"
  },
  "permissions": [
    "activeTab",
    "clipboardWrite"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "/content_scripts/modifyCSS.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "contextmenu.html",
    "css/contextmenu.css",
    "js/menuListener.js",
    "js/optionsListener.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{da0ef52f-95e9-487a-ab02-f4f35cfb7f59}"
    }
  }
}