refactor(algorithms, intervals, count days): add return type

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

Author: BrianLusina

algorithms/intervals/count_days/__init__.py

@@ -1,7 +1,7 @@
 from typing import List
 
 
-def count_days(days: int, meetings: List[List[int]]):
+def count_days(days: int, meetings: List[List[int]]) -> int:
     """
     Counts the number of days the employee is available for work but has no scheduled meetings.