Examine source code of Descomplicando

{
  "manifest_version": 2,
  "name": "Descomplicando",
  "version": "1.0.0",
  "applications": {
    "gecko": {
      "id": "ed.mi.goveia@gmail.com"
    }
  },
  "permissions": [
    "activeTab",
    "http://*/*",
    "https://*/*"
  ],
  "description": "Adaptação para o Firefox",
  "icons": {
    "48": "skull.png"
  },
  "browser_action": {
    "default_icon": "skull.png",
    "default_title": "Descomplicando",
    "default_popup": "index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "app.js"
      ]
    }
  ]
}