Examine source code of Amazon Earliest Delivery Date Auto-Selector

{
  "manifest_version": 2,
  "author": "ElRaphik",
  "developer": {
    "name": "ElRaphik",
    "url": "https://github.com/ElRaphik"
  },
  "name": "Amazon Earliest Delivery Date Auto-Selector",
  "short_name": "AEDDAS",
  "version": "0.0.0",
  "description": "Automatically selects earliest delivery option on Amazon checkout page.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.amazon.ae/checkout/*",
        "*://*.amazon.ca/checkout/*",
        "*://*.amazon.cn/checkout/*",
        "*://*.amazon.co.jp/checkout/*",
        "*://*.amazon.co.uk/checkout/*",
        "*://*.amazon.com/checkout/*",
        "*://*.amazon.com.au/checkout/*",
        "*://*.amazon.com.be/checkout/*",
        "*://*.amazon.com.br/checkout/*",
        "*://*.amazon.com.tr/checkout/*",
        "*://*.amazon.com.mx/checkout/*",
        "*://*.amazon.de/checkout/*",
        "*://*.amazon.es/checkout/*",
        "*://*.amazon.eg/checkout/*",
        "*://*.amazon.fr/checkout/*",
        "*://*.amazon.in/checkout/*",
        "*://*.amazon.it/checkout/*",
        "*://*.amazon.nl/checkout/*",
        "*://*.amazon.pl/checkout/*",
        "*://*.amazon.sa/checkout/*",
        "*://*.amazon.se/checkout/*",
        "*://*.amazon.sg/checkout/*",
        "*://*.amazon.co.za/checkout/*"
      ],
      "js": [
        "earlydateSelector.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7b83c59b-38a0-4e24-94ba-dab2426f0684}"
    }
  }
}