Added nn.SiLU activation

[ffs333]

Added nn.SiLU actication

Since PyTorch version only supports beta = 1.0 (no argument for beta), TF version with only beta=1.0

@converter(F.silu, channel_ordering_strategy=ChannelOrderingStrategy.MINIMUM_TRANSPOSITIONS)
def converter_silu(input: Tensor, inplace=False):
    def func(input: Tensor, inplace=False):
        return tf.nn.silu(input, beta=1.0)
    return func

nn.SiLU() (inplace=False default argument value)