Examine source code of Save To Spotify

{
  "manifest_version": 2,
  "name": "Save To Spotify",
  "version": "0.1.2",
  "description": "Save the currently playing song from popular music sites to your Spotify playlists or Liked Songs.",
  "browser_action": {
    "default_title": "Save To Spotify",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true,
    "open_in_tab": false
  },
  "permissions": [
    "storage",
    "identity",
    "tabs",
    "https://api.spotify.com/*",
    "https://accounts.spotify.com/*",
    "https://*.youtube.com/*",
    "https://youtu.be/*",
    "https://music.youtube.com/*",
    "https://soundcloud.com/*",
    "https://*.soundcloud.com/*",
    "https://music.apple.com/*",
    "https://music.amazon.com/*",
    "https://www.deezer.com/*",
    "https://www.pandora.com/*",
    "https://listen.tidal.com/*",
    "https://tidal.com/*",
    "https://bandcamp.com/*",
    "https://*.bandcamp.com/*",
    "https://open.spotify.com/*",
    "https://www.shazam.com/*",
    "https://shazam.com/*"
  ],
  "web_accessible_resources": [
    "popup.html",
    "popup.css",
    "popup.js",
    "icons/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.youtube.com/*",
        "https://youtu.be/*",
        "https://music.youtube.com/*",
        "https://soundcloud.com/*",
        "https://*.soundcloud.com/*",
        "https://music.apple.com/*",
        "https://music.amazon.com/*",
        "https://www.deezer.com/*",
        "https://www.pandora.com/*",
        "https://listen.tidal.com/*",
        "https://tidal.com/*",
        "https://bandcamp.com/*",
        "https://*.bandcamp.com/*",
        "https://open.spotify.com/*",
        "https://www.shazam.com/*",
        "https://shazam.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": false
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "saveto-spotify@livestream",
      "strict_min_version": "91.0"
    }
  }
}