Add boolean examples (#27)

Author: taseikyo

basics/boolean_example.py

@@ -8,6 +8,10 @@ def main():
     False
     >>> 3 < 4
     True
+    >>> 3 < 4 < 5
+    True
+    >>> 3 < 4 > 5
+    False
 
     >>> name = "Python"
     >>> age = 29
@@ -42,6 +46,10 @@ def main():
     True
     >>> bool("hi")
     True
+    >>> bool([])
+    False
+    >>> bool([''])
+    True
     """