Examine source code of Ghost Image Hover

{
  "manifest_version": 2,
  "name": "Ghost Image Hover",
  "version": "1.0",
  "description": "On hover, image fades to reveal a grayscale 'ghost' version behind it.",
  "permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{90fa2f2c-4c09-44b9-b64e-c35c8127fe3f}"
    }
  }
}