Add udl book as community use case

README.md

@@ -27,6 +27,7 @@ Quickstart and use cases
 * Community use cases
   * [TSNE: compare clustering of MNIST-1D vs. MNIST](https://colab.research.google.com/drive/1gUHCFoDd9pKbleyo3WOOPZtP3w5tH_fD?usp=sharing) (by [Dmitry Kobak](https://twitter.com/hippopedoid))
   * [A from-scratch, Numpy-only MLP with handwritten backprop](https://colab.research.google.com/drive/1E4w9chTkK-rPK-Zl-D0t4Q3FrdpQrHRQ?usp=sharing)
+  * [Simon Prince's _Understanding Deep Learning_](https://udlbook.github.io/udlbook/) textbook uses MNIST1D as a core teaching example
   * Send me a Colab link to your experiment and I'll feature it here.