Add some extra type hints

Author: Hugo Osvaldo Barrera

vdirsyncer/utils.py

@@ -108,9 +108,8 @@ class can take, and ``required`` is the subset of arguments the class
     return all, required
 
 
-def checkdir(path, create=False, mode=0o750):
-    """
-    Check whether ``path`` is a directory.
+def checkdir(path: str, create: bool = False, mode: int = 0o750) -> bool:
+    """Check whether ``path`` is a directory.
 
     :param create: Whether to create the directory (and all parent directories)
         if it does not exist.