mkdir borderify
cd borderify

{

  "manifest_version": 2,
  "name": "Borderify",
  "version": "1.0",
 
  "description": "Adiciona un borde rojo a todas las paginas que calcen con mozilla.org.",

  "icons": {
    "48": "icons/border-48.png"
  },

  "content_scripts": [
    {
      "matches": ["*://*.mozilla.org/*"],
      "js": ["borderify.js"]
    }
  ]

}