Examine source code of Heraldo Clean

{
  "manifest_version": 2,
  "name": "HeraldoClean",
  "version": "1.0.3",
  "description": "Elimina la publicidad de heraldo.es",
  "icons": {
    "48": "icons/logo-30-48.png",
    "96": "icons/logo-30-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.heraldo.es/*"
      ],
      "js": [
        "heraldoclean.js"
      ]
    }
  ]
}