Examine source code of CSS Override

{
  "description": "Adds a browser action to toggle applying CSS to pages.",
  "manifest_version": 2,
  "name": "CSS Override",
  "version": "1.0",
  "homepage_url": "https://github.com/swcolegrove/css-override-web-extension",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/css16.png",
      "48": "icons/css48.png",
      "96": "icons/css96.png"
    },
    "browser_style": true,
    "default_popup": "popup/menu.html"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage",
    "<all_urls>"
  ],
  "icons": {
    "48": "icons/css48.png",
    "96": "icons/css96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "css-override@scottco.co"
    }
  }
}