Examine source code of Typewriter Sound

{
  "manifest_version": 2,
  "name": "Typewriter Sound",
  "version": "1.0",
  "description": "Plays a vintage typewriter 'click' sound when typing in input fields and contenteditable areas.",
  "permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ae7f5634-732a-4224-aff0-a8cc4c4602e9}"
    }
  }
}