Add solution for rot13

src/python/katas/py5kyu/rot13.py

@@ -0,0 +1,15 @@
+"""Kata url: https://www.codewars.com/kata/52223df9e8f98c7aa7000062."""
+
+from string import ascii_lowercase
+
+def _rot13_char(c):
+    p = ascii_lowercase.find(c.lower())
+    if p == -1:
+        return c
+
+    l = ascii_lowercase[(p + 13) % len(ascii_lowercase)]
+    return l if c.islower() else l.upper()
+
+
+def rot13(message):
+    return ''.join(map(_rot13_char, message))