Examine source code of PerfectPixel PM

{
  "manifest_version": 2,
  "name": "PerfectPixel",
  "version": "1.3",
  "description": "Overlay images on top of websites to compare and ensure pixel-perfect accuracy.",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_popup": "overlay.html",
    "default_icon": {
      "32": "icons/logo_32.png",
      "64": "icons/logo_64.png",
      "128": "icons/logo_128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "overlay.css"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6fe05273-1512-4313-95bb-bbe4b6534e98}"
    }
  }
}