add access to SmartHint of TextBox, PasswordBox etc (place holder text) for set HorizontalAlignment

[mohsen-id]

for now we have to use: <TextBox> <TextBox.Resources> <Style TargetType="materialDesign:SmartHint" > <Setter Property="HorizontalAlignment" Value="Center"/> </Style> </TextBox.Resources> </TextBox>

and you could add property like: <TextBox materialDesign:PlaceHolder.HorizontalAlignment="Center" />

HintAssist.FloatingHintHorizontalAlignment effect when the text will flot.