Examine source code of GB Overlay

{
  "manifest_version": 2,
  "name": "Meu Overlay",
  "version": "1.0",
  "description": "Aplica um overlay à tela do navegador.",
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "overlay.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "applications": {
    "gecko": {
      "id": "meu-overlay@exemplo.com",
      "strict_min_version": "42.0"
    }
  }
}