Examine source code of Lyrics for YouTube

{
  "manifest_version": 2,
  "version": "0.1.2resigned1",
  "name": "Lyrics for YouTube",
  "description": "A player button to load embedded lyrics of the current track in YouTube",
  "icons": {
    "16": "data/icons/16.png",
    "32": "data/icons/32.png",
    "48": "data/icons/48.png",
    "64": "data/icons/64.png",
    "128": "data/icons/128.png",
    "256": "data/icons/256.png"
  },
  "permissions": [
    "storage",
    "*://api.musixmatch.com/*"
  ],
  "homepage_url": "https://add0n.com/youtube-tools.html?from=lyrics",
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "data/inject.js"
      ],
      "css": [
        "data/inject.css"
      ],
      "run_at": "document_start",
      "all_frames": false
    }
  ],
  "background": {
    "persistent": false,
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6d6c5d1e-a4f1-4955-af2a-2818cf104a47}"
    }
  }
}