Added to maths and strings (#1642)

* Added to maths and strings

* added changes suggest by cclauss

strings/lower.py

@@ -0,0 +1,29 @@
+def lower(word: str) -> str:
+
+    """ 
+    Will convert the entire string to lowecase letters 
+    
+    >>> lower("wow")
+    'wow'
+    >>> lower("HellZo")
+    'hellzo'
+    >>> lower("WHAT")
+    'what'
+    
+    >>> lower("wh[]32")
+    'wh[]32'
+    >>> lower("whAT")
+    'what'
+    """
+
+    # converting to ascii value int value and checking to see if char is a capital letter
+    # if it is a capital letter it is getting shift by 32 which makes it a lower case letter
+    return "".join(
+        chr(ord(char) + 32) if 65 <= ord(char) <= 90 else char for char in word
+    )
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()