code: @Nonnull
    public JSVar param (@Nonnull @Nonempty final String sName)
    {
      final JSVar aVar = new JSVar (sName, null);
      m_aParams.add (aVar);
      return aVar;
    }
docs: Add the specified variable to the list of parameters for this function
  signature.
  
  @param sName
  Name of the parameter being added
  @return New parameter variable