RNN constructor
Implementation
RNN(this.inputSize, this.hiddenSize, this.outputSize) {
Wx = Matrix2d(hiddenSize, inputSize);
Wh = Matrix2d(hiddenSize, hiddenSize);
Wy = Matrix2d(outputSize, hiddenSize);
bh = ValueVector(List.generate(hiddenSize, (_) => Value(0)));
by = ValueVector(List.generate(outputSize, (_) => Value(0)));
}