Examine source code of Snek 2 - A Snake Game

{
  "manifest_version": 2,
  "name": "Snake Game",
  "version": "2.4",
  "description": "A simple Snake game as a Firefox extension",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "index.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{dea03ec1-b728-4824-a049-bdf7c1700619}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}