Examine source code of Nolean YouTube Overlay

{
  "manifest_version": 2,
  "name": "Nolean Overlay",
  "version": "1.0",
  "description": "Overlays a PNG on all YouTube thumbnails.",
  "permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    "noleanpng.png",
    "nogreenpng.png"
  ],
  "icons": {
    "48": "noleanpng48.png",
    "96": "noleanpng96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "nolean@hijo.com",
      "strict_min_version": "58.0"
    }
  }
}