Examine source code of Link Destination Preview

{
  "manifest_version": 2,
  "name": "Link Destination Preview",
  "version": "1.0.0",
  "description": "Hover any link to instantly see where it really goes — full URL, HTTPS status, external site warning, and file type detection.",
  "author": "brian",
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "link-destination-preview@brian",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}