Examine source code of PicFlip

{
  "manifest_version": 3,
  "name": "PicFlip",
  "description": "Save time crosslisting. Download listing photos in one click.",
  "version": "1.0.0",
  "permissions": [
    "downloads",
    "activeTab",
    "tabs",
    "scripting"
  ],
  "host_permissions": [
    "*://*.ebay.com/*",
    "*://*.ebay.co.uk/*",
    "*://*.ebay.ca/*",
    "*://*.ebay.de/*",
    "*://*.ebay.fr/*",
    "*://*.ebay.it/*",
    "*://*.ebay.es/*",
    "*://*.ebay.com.au/*",
    "*://*.ebay.at/*",
    "*://*.ebay.ch/*",
    "*://*.ebay.ie/*",
    "*://*.ebay.be/*",
    "*://*.ebay.nl/*",
    "*://*.ebay.pl/*",
    "*://*.ebay.se/*",
    "*://*.ebay.com.sg/*",
    "*://*.ebay.com.hk/*",
    "*://*.ebay.com.my/*",
    "*://*.ebay.com.ph/*",
    "*://i.ebayimg.com/*",
    "*://*.ebayimg.com/*",
    "*://img.auctiva.com/*",
    "*://*.mercari.com/*",
    "*://*.mercdn.net/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "picflip@joyex.com",
      "strict_min_version": "109.0"
    },
    "background": {
      "scripts": [
        "background.js"
      ]
    },
    "action": {
      "default_title": "Download Listing Photos",
      "default_icon": {
        "128": "icon-enabled.png"
      }
    },
    "icons": {
      "128": "icon-enabled.png"
    }
  }
}