Examine source code of Image URL Overlay

{
  "manifest_version": 2,
  "name": "Image URL Overlay",
  "version": "1.0.4",
  "author": "David Cordero",
  "description": "Show an overlay with the image URL on each image.",
  "icons": {
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "128": "icons/icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e31a24fc-61fb-49d5-a2c6-69abf80fd63b}"
    }
  }
}