Examine source code of Tap Counter

{
  "manifest_version": 2,
  "name": "Tap Counter",
  "version": "0.1.5",
  "description": "Multi-counter tap tracker by MeenTek. Create named counters, tap or press Space to count, undo mistakes, reset with confirmation, and delete with the Del key. All counts saved automatically.",
  "author": "MeenTek",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_title": "Tap Counter",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon.png",
      "48": "icon.png",
      "128": "icon.png"
    }
  },
  "icons": {
    "16": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{21e844f8-78d9-4dac-8df5-7dda73858a58}"
    }
  }
}