Examine source code of Resonance for Spotify

{
  "manifest_version": 3,
  "browser_specific_settings": {
    "gecko": {
      "id": "resonance@resonance.com",
      "strict_min_version": "58.0"
    }
  },
  "name": "Resonance",
  "icons": {
    "16": "logo.png",
    "32": "logo.png",
    "48": "logo.png",
    "128": "logo.png"
  },
  "version": "1.1.3",
  "description": "Rate your favorite Spotify tracks effortlessly",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "js": [
        "content.js",
        "user.js"
      ],
      "css": [
        "style.css",
        "user.css"
      ],
      "matches": [
        "https://open.spotify.com/*"
      ]
    }
  ]
}