Function once

once<T>(eventType, callback): (() => void)
Subscribe to an event that will automatically unsubscribe after the first occurrence
Type Parameters
- T = ApiCallback<string>
Parameters
- eventType: string
  The event type to listen for
- callback: EventCallback<T>
  The callback to execute once
Returns (() => void)
Unsubscribe function
- - (): void
  - Returns void