Examine source code of Typing Sound Effect

{
  "manifest_version": 2,
  "name": "Typing Sound Effect",
  "version": "1.2",
  "description": "Plays sounds when typing.",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "sounds/ENTER.mp3",
    "sounds/Backwards.mp3",
    "sounds/Keypress1.mp3",
    "sounds/Keypress2.mp3",
    "sounds/Keypress3.mp3",
    "sounds/Keypress4.mp3",
    "sounds/Keypress5.mp3"
  ],
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{99cdc3ec-fafc-4a3b-99c6-7be9fa08c456}"
    }
  }
}