Examine source code of Check and Display

{
  "description": "check and display travel theme to users, which is the latest upgraded version",
  "icons": {
    "48": "icons/logo_48.png",
    "64": "icons/logo_64.png"
  },
  "manifest_version": 2,
  "name": "Check and Display",
  "permissions": [
    "alarms",
    "theme"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "version": "1.0",
  "applications": {
    "gecko": {
      "strict_min_version": "59.0a2",
      "id": "{e0daa933-4ffb-4c5e-9e8f-8b53bad40927}"
    }
  }
}