Examine source code of Spotube - #1 Spotify extension

{
  "name": "Spotube - #1 Spotify extension",
  "version": "3.2",
  "manifest_version": 2,
  "description": "An extension for easily adding YouTube songs to your Spotify playlists.",
  "page_action": {
    "default_icon": "icon-128.png",
    "default_popup": "popup.html",
    "default_title": "Spotube - #1 Spotify extension"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*",
        "*://*.soundcloud.com/*"
      ],
      "js": [
        "content.js"
      ]
    },
    {
      "matches": [
        "*://*.youtube.com/?code*"
      ],
      "js": [
        "libs/oauth/injection.js"
      ],
      "run_at": "document_start"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "icons": {
    "128": "icon-128.png"
  },
  "web_accessible_resources": [
    "libs/*/*"
  ]
}