Examine source code of Towster - Reward yourself

{
  "name": "Towster - Reward yourself",
  "description": "Shop discounts on the Qantas Rewards Store without loyalty points",
  "version": "0.0.1",
  "short_name": "Towster",
  "homepage_url": "https://towster.co/",
  "manifest_version": 2,
  "minimum_chrome_version": "74",
  "browser_specific_settings": {
    "gecko": {
      "id": "ryan.soury@towster.co"
    }
  },
  "permissions": [
    "activeTab",
    "tabs",
    "https://www.qantasstore.com.au/*",
    "https://staging.towster.co/*",
    "https://towster.co/*"
  ],
  "optional_permissions": [
    "*://*/*"
  ],
  "icons": {
    "16": "images/icon-16.png",
    "128": "images/icon-128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "19": "images/greyscale-icon-19.png",
      "38": "images/greyscale-icon-38.png"
    },
    "default_title": "Towster"
  },
  "content_scripts": [
    {
      "run_at": "document_start",
      "match_about_blank": false,
      "all_frames": false,
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "css": [],
      "js": [
        "towster.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "towster-runnable.js"
  ]
}