Examine source code of Word Counter

{
  "manifest_version": 3,
  "name": "Word Counter",
  "version": "1.0",
  "description": "Word counter with ease.",
  "action": {
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "popup.html"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "word-counter@unique.extension.id"
    }
  }
}