Examine source code of ProxySwitcheroo

{
  "manifest_version": 2,
  "name": "ProxySwitcheroo",
  "version": "1.0.1",
  "description": "Simple and Safe Proxy Switching",
  "icons": {
    "256": "icons/globe.png"
  },
  "permissions": [
    "storage",
    "proxy"
  ],
  "browser_action": {
    "default_icon": "icons/globe-disabled.png",
    "default_title": "No Proxy"
  },
  "options_ui": {
    "page": "options.html"
  },
  "applications": {
    "gecko": {
      "id": "{6787c9e3-c787-4e21-9449-92e301642b34}",
      "strict_min_version": "60.0"
    }
  },
  "background": {
    "scripts": [
      "defaults.js",
      "background.js"
    ]
  }
}