Examine source code of Piano Virtual Keyboard

{
  "manifest_version": 2,
  "name": "Piano Virtual Keyboard",
  "version": "1.0",
  "description": "Play a virtual piano keyboard from your browser.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Piano Virtual Keyboard"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{fea89633-c8a5-403d-b803-bb12b6d57218}"
    }
  }
}