Examine source code of School Year Calculator

{
  "manifest_version": 2,
  "name": "School Year Calculator",
  "description": "Convert date of birth to school year and 'Ux' label",
  "version": "1.7",
  "author": "David Lomas",
  "icons": {
    "16": "images/date16.png",
    "19": "images/date19.png",
    "32": "images/date32.png",
    "38": "images/date38.png",
    "48": "images/date48.png",
    "128": "images/date128.png"
  },
  "browser_action": {
    "default_title": "School Year Calculator",
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/date16.png",
      "19": "images/date19.png",
      "32": "images/date32.png",
      "38": "images/date38.png",
      "48": "images/date48.png",
      "128": "images/date128.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{43510c51-5453-407b-811b-d1ae4d12831f}"
    }
  }
}