Examine source code of Sync My Unit

{
  "manifest_version": 2,
  "name": "Sync My Unit",
  "version": "1.0",
  "description": "Syncs units from freddybushboy.github.io/unit-cards/ via Firefox Sync",
  "icons": {
    "32": "icons/freddy-32.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://freddybushboy.github.io/unit-cards/"
      ],
      "js": [
        "sync.js"
      ]
    }
  ],
  "permissions": [
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "ammut@syncmyunit.ch"
    }
  }
}