Examine source code of Crossword Completion Song

{
  "manifest_version": 2,
  "name": "Crossword Completion Song",
  "version": "1.0",
  "description": "Plays a song when a crossword is completed on downforacross.com.",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://api.foracross.com/api/record_solve/*",
    "*://*.downforacross.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.downforacross.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "San_Jose_Strut.mp3"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{92c38472-d91e-4f87-8340-19a8f1ffd1cf}"
    }
  }
}