Examine source code of Bitcoin Block Height

{
  "manifest_version": 2,
  "name": "Bitcoin Block Height",
  "version": "1.0.0",
  "description": "Live Bitcoin block height and latest block info from mempool.space, updated every 5 minutes.",
  "browser_specific_settings": {
    "gecko": {
      "id": "bitcoin-block-height-tracker@extension",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "storage",
    "https://mempool.space/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Bitcoin Block Height",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "96": "icons/icon96.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  }
}