Examine source code of FocusSound

{
  "manifest_version": 2,
  "name": "FocusSound",
  "version": "1.0",
  "description": "Micro-loops (rain, white noise, hum) with Pomodoro timers, fade in/out, and mixing tracks using Web Audio. All generated locally.",
  "icons": {
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "browser_action": {
    "default_title": "FocusSound",
    "default_popup": "focussound.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{d9550454-067b-4bc9-bffc-fb456d93d7ed}"
    }
  }
}