Examine source code of Learn Swift basics

{
  "manifest_version": 2,
  "name": "Swift Language Learning",
  "version": "1.0.0",
  "description": "Learn Swift basics with short lessons, flashcards and quizzes directly from the browser popup.",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_title": "Swift Language Learning",
    "default_popup": "popup.html"
  },
  "applications": {
    "gecko": {
      "id": "swift-language-learning@example.com"
    }
  }
}