Adding mnist_acgan.py example link in README (#4876)

examples/README.md

@@ -48,6 +48,9 @@ Compares different LSTM implementations on the IMDB sentiment classification tas
 [lstm_text_generation.py](lstm_text_generation.py)
 Generates text from Nietzsche's writings.
 
+[mnist_acgan.py](mnist_acgan.py)
+Implementation of AC-GAN ( Auxiliary Classifier GAN ) on the MNIST dataset
+
 [mnist_cnn.py](mnist_cnn.py)
 Trains a simple convnet on the MNIST dataset.