Function subscribe

subscribe(subscriber: (userAction: UserActionTracker) => void): () => void
Safe wrapper for dynatrace.userActions.subscribe which reverts to a noop if RUM JavaScript or the user actions module is not available.
Parameters
- subscriber: (userAction: UserActionTracker) => void
  A callback function that is called whenever Dynatrace creates a new user action.
Returns () => void
An unsubscriber function to remove the subscription, or undefined if the user actions module is not enabled.
Example
```
import * as userActions from "@dynatrace/rum-javascript-sdk/api/user-actions";
const unsubscribe = userActions.subscribe((userAction) => {
    console.log('New user action created');
    userAction.completeAutomatically = false;
});
// later
unsubscribe?.();
```