Examine source code of Gmail Cycle

{
  "manifest_version": 2,
  "name": "Gmail Cycle",
  "version": "1.0",
  "description": "Schedule and send repeating emails via Gmail with ease.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "storage",
    "identity"
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1ce5bc33-8481-48b7-a511-af5ea9223b27}"
    }
  }
}