Examine source code of Word Chain Puzzle

{
  "manifest_version": 2,
  "name": "Word Chain Puzzle",
  "description": "Build a chain of real words from the start word to the target, changing one letter per link. Shows how many links remain at every point and rates your finished chain against the shortest possible one.",
  "version": "6.9",
  "browser_specific_settings": {
    "gecko": {
      "id": "{e7bd8e04-6f48-4bde-9ca4-21f533f0af9b}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "32": "graphics/icon-32.png",
    "48": "graphics/icon-48.png",
    "64": "graphics/icon-64.png",
    "96": "graphics/icon-96.png",
    "128": "graphics/icon-128.png"
  },
  "browser_action": {
    "default_title": "Word Chain Puzzle",
    "default_popup": "popup.html",
    "default_icon": {
      "32": "graphics/icon-32.png",
      "48": "graphics/icon-48.png",
      "64": "graphics/icon-64.png"
    }
  },
  "permissions": [
    "storage"
  ]
}