Examine source code of Simple Calculator 1

{
  "manifest_version": 2,
  "name": "Simple Calculator",
  "version": "1.0",
  "description": "A basic calculator extension for Firefox.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/calculator-16.png",
      "48": "icons/calculator-48.png",
      "128": "icons/calculator-128.png"
    }
  },
  "icons": {
    "16": "icons/calculator-16.png",
    "48": "icons/calculator-48.png",
    "128": "icons/calculator-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ac1a9f0c-6c6c-4c7d-af90-fdf2347de20f}"
    }
  }
}