Function unregistration

unregistration(listenerId, fn): void
JMap.Event.Extension.on.unregistration

This event is triggered when an extension is unregistered.
Parameters
- listenerId: string
  Your listener id (must be unique)
- fn: ((params) => void)
  Your listener function
  - - (params): void
    - Parameters
      params: JExtensionEventParams
      Returns void
Returns void
Example
```
// log a message in the console each time an extension has been unregistered
JMap.Event.Extension.on.unregistration(
  "custom-core-extension-unregistration",
  params => console.log(`Extension id="${params.extensionId}" has been unregistered`)
)
```