add this function showNextButton

RCTTextFieldManager.m

RCT_CUSTOM_VIEW_PROPERTY(showNextButton, BOOL, RCTTextField)
{
  if (json && ([RCTConvert BOOL:json])) {
    UIToolbar* toolbar = [[UIToolbar alloc] init];
    [toolbar sizeToFit];
    UIBarButtonItem* flex = [[UIBarButtonItem alloc]
                             initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace
                             target:nil action:nil];
    UIBarButtonItem* doneButton = [[UIBarButtonItem alloc]
                                   initWithTitle:@"Next" style:(UIBarButtonItemStylePlain)
                                   target:view action:@selector(endEditing:)];

    
    toolbar.items = @[flex, doneButton];
    view.inputAccessoryView = toolbar;
  } else {
    view.inputAccessoryView = nil;
  }
}