Examine source code of Track Number Hub

{
  "manifest_version": 2,
  "name": "Track Number Hub",
  "version": "5.2",
  "description": "Finds postal and courier tracking numbers in page text, checks the S10 check digit and builds the tracking link for you.",
  "browser_specific_settings": {
    "gecko": {
      "id": "{d7eef822-c371-4006-a7a5-77de46346247}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "32": "graphics/icon-32.png",
    "48": "graphics/icon-48.png",
    "64": "graphics/icon-64.png",
    "96": "graphics/icon-96.png",
    "128": "graphics/icon-128.png"
  },
  "browser_action": {
    "default_title": "Track Number Hub",
    "default_popup": "scripts/popup.html",
    "default_icon": {
      "32": "graphics/icon-32.png",
      "48": "graphics/icon-48.png",
      "64": "graphics/icon-64.png",
      "96": "graphics/icon-96.png",
      "128": "graphics/icon-128.png"
    }
  },
  "permissions": [
    "storage",
    "activeTab"
  ]
}