Examine source code of PixelSpotter

{
  "manifest_version": 2,
  "name": "PixelSpotter",
  "version": "1.0",
  "description": "Show pixel coordinates and color (RGB/HEX) on image hover.",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{06d7739c-fac4-44f4-9a8d-ae69cb3f9d37}"
    }
  }
}