Breathe

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Breathe",
  "version": "1.2.0",
  "description": "A Firefox WebExtension reminding you to breathe, or anything else.",
  "icons": {
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "options_ui": {
    "page": "settings/settings.html"
  },
  "permissions": [
    "storage"
  ]
}