[Book] Add scikit test

Type : fix.

Abstract:
* Add scikit test

ch03/scikit_learb_test.py

@@ -0,0 +1,16 @@
+from sklearn import datasets
+from sklearn.model_selection import train_test_split
+from sklearn.preprocessing import StandardScaler
+import numpy as np
+
+iris = datasets.load_iris()
+X = iris.data[:, [2, 3]]
+y = iris.target
+print(f"Class labels : {np.unique(y)}")
+
+X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.3, random_state=1, stratify=y)
+
+sc = StandardScaler()
+sc.fit(X_train)
+X_train_std = sc.transform(X_train)
+X_test_std = sc.transform(X_test)