Examine source code of responsivo

{
  "name": "responsivo",
  "version": "0.0.7",
  "description": "A web extension. Displays multiple view widths at once.",
  "manifest_version": 2,
  "icons": {
    "128": "128.png"
  },
  "permissions": [
    "<all_urls>",
    "activeTab",
    "http://*/*",
    "https://*/*",
    "storage",
    "webNavigation",
    "webRequest",
    "webRequestBlocking"
  ],
  "browser_action": {
    "default_title": "responsivo",
    "default_icon": {
      "128": "128.png"
    },
    "browser_style": false
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{66457214-20ac-429c-8130-a0b3246e6df7}"
    }
  }
}