Examine source code of HBOImprovedSubs

{
  "manifest_version": 2,
  "name": "HBOImprovedSubs",
  "version": "1.0",
  "description": "Better subtitles style for HBO video player.",
  "content_scripts": [
    {
      "matches": [
        "*://*.hboespana.com/*"
      ],
      "css": [
        "subs_style.css"
      ]
    }
  ]
}