Examine source code of The BMI Calculator

{
  "manifest_version": 2,
  "name": "BMI Calculator",
  "version": "1.1",
  "description": "A simple BMI calculator based on age with units changeable to pounds and kilograms.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon16.png",
      "48": "images/icon48.png",
      "128": "images/icon128.png"
    }
  },
  "permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{70612073-24c7-4cbe-b140-fc439e2de7cb}"
    }
  }
}