Examine source code of Wikington Crescent Score

{
  "manifest_version": 2,
  "name": "Mornington Crescent",
  "version": "1.0.0",
  "description": "Count Wikipedia pages until you reach Mornington Crescent tube station.",
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "browsingActivity",
          "websiteContent"
        ]
      },
      "id": "{711833dc-284d-40ea-9f78-d4ac60a6fe40}"
    }
  },
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "48": "icons/icon48.png"
    },
    "default_title": "Mornington Crescent"
  },
  "background": {
    "scripts": [
      "background/background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.wikipedia.org/wiki/*"
      ],
      "js": [
        "content/content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "tabs",
    "storage",
    "*://*.wikipedia.org/*"
  ]
}