Examine source code of Breathe

{
  "manifest_version": 2,
  "name": "Breathe",
  "version": "1.2.1resigned1",
  "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"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{bb2858bb-fa71-4e1a-836a-4d17df7e01c8}"
    }
  }
}