Examine source code of Gallery Saver

{
  "manifest_version": 2,
  "name": "Gallery Saver",
  "version": "1.0",
  "description": "Easily view and download all images from the current webpage.",
  "browser_specific_settings": {
    "gecko": {
      "id": "{cd4a0b36-1340-44a1-b52d-c80dcf29644b}",
      "strict_min_version": "122.0"
    }
  },
  "background": {
    "scripts": [
      "background_gallery.js"
    ]
  },
  "browser_action": {
    "default_icon": "icon64.png",
    "default_title": "Save Images",
    "default_popup": "popup_gallery.html"
  },
  "permissions": [
    "activeTab",
    "downloads"
  ],
  "icons": {
    "64": "icon64.png",
    "128": "icon128.png"
  }
}