Examine source code of Apple Music RP

{
  "manifest_version": 2,
  "name": "Apple Music RP",
  "version": "2",
  "description": "Display Song Title, Artist and some more Information of the Song you're currently listening to on Apple Music.",
  "icons": {
    "48": "icons/icon-48.png"
  },
  "permissions": [
    "*://localhost/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://music.apple.com/*"
      ],
      "js": [
        "main.js"
      ]
    }
  ]
}