Add CSS class to the label of a group

[tortuetorche]

Usage with Laravel and Bootstrap 4:

{!! Former::open()->method('GET') !!}
    {!! Former::text('foo')->addLabelClass('bar') !!}
{!! Former::close() !!}

Will produce:

<form accept-charset="utf-8" class="form-horizontal" method="GET">
  <div class="form-group row">
    <label for="foo" class="bar col-form-label col-lg-2 col-sm-4">Foo</label>
    <div class="col-lg-10 col-sm-8">
      <input class="form-control" id="foo" type="text" name="foo">
    </div>
  </div>
</form>