Added documentation examples for nonlocal-and-global. (#6880)

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

Author: mbyrnepr2

doc/data/messages/n/nonlocal-and-global/bad.py

@@ -0,0 +1,11 @@
+NUMBER = 42
+
+
+def update_number(number):  # [nonlocal-and-global]
+    global NUMBER
+    nonlocal NUMBER
+    NUMBER = number
+    print(f"New global number is: {NUMBER}")
+
+
+update_number(24)

doc/data/messages/n/nonlocal-and-global/details.rst

@@ -1 +1,10 @@
-# This is a placeholder for correct code for this message.
+NUMBER = 42
+
+
+def update_number(number):
+    global NUMBER
+    NUMBER = number
+    print(f"New global number is: {NUMBER}")
+
+
+update_number(24)