Examine source code of In Spotify

{
  "manifest_version": 3,
  "name": "In Spotify",
  "version": "1.0",
  "description": "Opens Spotify links in the desktop app instead of the web player.",
  "permissions": [
    "storage",
    "webRequest",
    "tabs",
    "webRequestBlocking"
  ],
  "host_permissions": [
    "*://open.spotify.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@in-spotify"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/spotify-in-16.png",
      "48": "icons/spotify-in-48.png",
      "128": "icons/spotify-in-128.png"
    }
  },
  "icons": {
    "16": "icons/spotify-in-16.png",
    "48": "icons/spotify-in-48.png",
    "128": "icons/spotify-in-128.png"
  }
}