Add palindrome check algorithm with reference URL

Author: Hbasu5

strings/is_palindrome.py

@@ -1,10 +1,19 @@
 def is_palindrome(text: str) -> bool:
     """
     Check if a string is a palindrome.
+
+    A palindrome is a word, number, phrase, or other sequence of 
+    characters which reads the same backward as forward.
+
+    Reference: https://en.wikipedia.org/wiki/Palindrome
+
+    Examples:
     >>> is_palindrome("radar")
     True
     >>> is_palindrome("hello")
     False
+    >>> is_palindrome("level")
+    True
     """
     return text == text[::-1]