Examine source code of Gumnotes

{
  "short_name": "gumnotes",
  "name": "Gumnotes",
  "description": "Write notes that stick",
  "version": "0.2",
  "manifest_version": 2,
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "128": "icons/icon-128.png",
    "512": "icons/icon-512.png"
  },
  "permissions": [
    "identity"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "hi@gumnotes.co"
    }
  }
}