Examine source code of Bitcoin Halving Countdown

{
  "manifest_version": 2,
  "name": "Bitcoin Halving Countdown",
  "version": "1.0",
  "description": "Displays the time until the next Bitcoin halving",
  "icons": {
    "48": "icon48.png",
    "96": "icon96.png"
  },
  "permissions": [
    "https://halvingbitcoins.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": {
      "48": "icon48.png",
      "96": "icon96.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d5148abe-104f-494b-a438-a35360226f56}"
    }
  }
}