功能: 计算神经网络Mish激活函数

格式: netFunByMish(x)

x : 为矩阵变量或者数值

说明:
1. 函数执行成功返回和x同纬度的矩阵变量

2. 本函数主要计算的原理如下
$$\mathbf{netFunByMish}(x_i) = x_i\tanh(\log(1 + \exp(x)))$$

例子:
x =
[-0.73290256607947   -1.95092696112158    0.21744714338213    2.19789781453921
 -4.72275318588258    1.99957438581603    2.94959032789319   -4.31942455462153
 -6.10488919615973   -1.19050327068684   -6.38943656901337    2.98098757280083
 -2.76742173278119   -4.81647247463300   -3.72662812435377   -4.00467786914887 ]
y = netFunByMish(x)//回车得到如下结果
y = 
[-0.27367842031844   -0.25777326918678    0.14533253724053    2.15442727611016
 -0.04180178141436    1.94350383742596    2.93502210281970   -0.05709847983768
 -0.01361047144717   -0.30884291640971   -0.01072014678418    2.96711577217730
 -0.16840872850003   -0.03883294111913   -0.08863479234795   -0.07234057528317 ]