Examine source code of Classic Google Icons

{
  "manifest_version": 2,
  "version": "1.5.0",
  "name": "Classic Google Icons",
  "description": "Use the pre-2020 Material Design icons for Google products like Gmail, Calendar, and Maps.",
  "author": "dangeredwolf",
  "icons": {
    "16": "Icon16.png",
    "24": "Icon24.png",
    "32": "Icon32.png",
    "48": "Icon48.png",
    "64": "Icon64.png",
    "128": "Icon128.png",
    "256": "Icon256.png",
    "512": "Icon512.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "https://*.gstatic.com/*",
    "https://*.google.com/*",
    "https://*.googleusercontent.com/*"
  ],
  "web_accessible_resources": [
    "images/*"
  ]
}