Examine source code of Dark Mode for Amazon

{
  "manifest_version": 2,
  "name": "DarkMode Amazon",
  "version": "1.3",
  "description": "DarkMode Amazon",
  "default_locale": "en",
  "browser_action": {
    "default_icon": {
      "16": "src/images/icon16.png",
      "32": "src/images/icon32.png",
      "48": "src/images/icon48.png",
      "64": "src/images/icon64.png",
      "128": "src/images/icon128.png"
    },
    "default_popup": "index.html"
  },
  "background": {
    "scripts": [
      "service-worker-loader.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.amazon.com/*",
        "*://*.amazon.co.uk/*",
        "*://*.amazon.de/*",
        "*://*.amazon.fr/*",
        "*://*.amazon.it/*",
        "*://*.amazon.es/*",
        "*://*.amazon.ca/*",
        "*://*.amazon.com.au/*",
        "*://*.amazon.com.br/*",
        "*://*.amazon.co.jp/*",
        "*://*.amazon.in/*",
        "*://*.amazon.com.mx/*",
        "*://*.amazon.nl/*",
        "*://*.amazon.pl/*",
        "*://*.amazon.sg/*",
        "*://*.amazon.sa/*",
        "*://*.amazon.ae/*",
        "*://*.amazon.se/*",
        "*://*.amazon.com.tr/*",
        "*://*.amazon.cn/*",
        "*://*.amazon.cz/*",
        "*://*.amazon.eg/*",
        "*://*.aboutamazon.eu/*"
      ],
      "css": [
        "styles.css"
      ],
      "js": [
        "content.js"
      ],
      "all_frames": true,
      "run_at": "document_start"
    }
  ],
  "icons": {
    "16": "src/images/icon16.png",
    "32": "src/images/icon32.png",
    "48": "src/images/icon48.png",
    "64": "src/images/icon64.png",
    "128": "src/images/icon128.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "web_accessible_resources": [
    "src/images/icon128.png",
    "assets/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ac2848ce-4e53-41e9-aeaa-20d8e2ec865a}"
    }
  }
}