Examine source code of Vocabulary Booster

{
  "manifest_version": 2,
  "name": "Vocabulary Booster",
  "version": "1.0",
  "description": "Show a new English word every day on new tab.",
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d0746f0a-a42c-45ca-b3ef-fd2877ec9e8f}"
    }
  }
}