Examine source code of Multi Timer

{
  "manifest_version": 2,
  "name": "Multi Timer",
  "description": "Run several named timers at once. The one finishing first counts down in the toolbar badge, each timer can repeat, and everything is stored as a deadline so nothing drifts while the popup is closed.",
  "version": "3.1.5.2",
  "browser_specific_settings": {
    "gecko": {
      "id": "{4c9f8a6b-ddf4-49bf-8388-2f5b77b8778d}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "browser_action": {
    "default_title": "Multi Timer",
    "default_popup": "popup.html",
    "default_icon": {
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "64": "icons/icon-64.png"
    }
  },
  "permissions": [
    "storage",
    "notifications",
    "alarms"
  ],
  "background": {
    "scripts": [
      "src/core.js",
      "src/background.js"
    ],
    "persistent": true
  }
}