Examine source code of Spotify Auto Zoom

{
  "manifest_version": 2,
  "name": "Spotify Auto Zoom",
  "version": "1.0",
  "description": "Automatically sets zoom to 90% for Spotify links.",
  "permissions": [
    "tabs",
    "https://open.spotify.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c35f4468-b45f-4c7a-aa70-c81a6ea87000}"
    }
  }
}