Examine source code of Simple Counter

{
  "manifest_version": 2,
  "name": "Simple Counter",
  "version": "1.0",
  "description": "A simple counter extension",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Simple Counter"
  },
  "commands": {
    "increment-counter": {
      "suggested_key": {
        "default": "Alt+2"
      },
      "description": "Increment the counter"
    },
    "decrement-counter": {
      "suggested_key": {
        "default": "Alt+1"
      },
      "description": "Decrement the counter"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2566177c-5e20-4cb2-8318-cc0aeb04fb4d}"
    }
  }
}