add link to the dataset (#44)

What data set to use? Week 3 Day 3 ex 5 #36

piscine/week03/day03/ex05/README.md

@@ -3,6 +3,7 @@
 The goal of this exercise is to learn to use a neural network to classify a multiclass data set. The data set used is the Iris data set which allows to classify flower given basic features as flower's measurement. 
 
 Preliminary: 
+    - [Load the dataset from `sklearn`.](https://scikit-learn.org/stable/auto_examples/datasets/plot_iris_dataset.html)
     - Split train test. Keep 20% for the test set. Use `random_state=1`. 
     - Scale the data using Standard Scaler
 
@@ -11,4 +12,4 @@ Preliminary:
 
 2. Train a neural network on the train set and predict on the test set. The neural network should have 1 hidden layers. The expected **accuracy** on the test set is minimum 90%.
 *Hint*: inscrease the number of epochs 
-**Warning**: Do no forget to evaluate the neural network on the **SCALED** test set. 
+**Warning**: Do no forget to evaluate the neural network on the **SCALED** test set.