title: ng-select prevent special characters on typeahead
body: <p>Using the ng-select library, is is possible to prevent special characters from being processed? Something akin to <a href="http://Controlar%20el%20ingreso%20de%20caracteres%20especiales%20de%20inicio,%20por%20ejemplo,%20espacios%20en%20blanco%20o%20arroba,%20o%20signos%20de%20puntuaci%C3%B3n.%20%20El%20unico%20caracter%20especial%20permitido%20es%20el%20guion%20y%20no%20de%20iniciio." rel="nofollow noreferrer">this</a> solution. </p>
  
  <p>I've tried multiple approaches, but it seems like whatever the typeahead value is isn't exposed and can't be modified. </p>
  
  <p>Is there any workaround to this? Even firing a <code>.next()</code> on the typeahead subject doesn't change what's shown on the view.</p>