Examine source code of Outbound Port Monitor

{
  "manifest_version": 2,
  "name": "Outbound Port Monitor",
  "version": "1.0",
  "description": "Sidebar that logs destination ports of the browser's own outgoing connections in real time, color coded by port range, with hostname, type, timestamp, export and clear. All client-side, no data collection.",
  "browser_specific_settings": {
    "gecko": {
      "id": "outbound_port_monitor@libor_benes.dev",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "sidebar_action": {
    "default_title": "Outbound Port Monitor",
    "default_panel": "sidebar.html"
  },
  "background": {
    "scripts": [
      "ports.js",
      "background.js"
    ],
    "persistent": true
  },
  "permissions": [
    "webRequest",
    "<all_urls>",
    "downloads"
  ]
}