Fixed multicharacter seperator bug

Author: Aman Mishra

strings/split.py

@@ -20,6 +20,8 @@ def split(string: str, separator: str = " ") -> list:
     """
 
     split_words = []
+    if(len(separator)>1):
+        raise ValueError("Separator must be a single character")
 
     last_index = 0
     for index, char in enumerate(string):