Examine source code of SetDate Nou

{
  "manifest_version": 2,
  "name": "SetDate Nou",
  "version": "1.0",
  "description": "Insere intervalo de data ao calendário",
  "icons": {
    "48": "icons/icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "app.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/icon.png",
    "default_title": "SetData Nou",
    "default_popup": "popup/page.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "wesley.souza@noufiscal.com.br"
    }
  }
}