Added feature to return macOS desktop path for StoragePath

[temitayoadefemi]

This pull request introduces a new feature to return the macOS desktop path for use in the StoragePath module. This addition allows access to the user's desktop directory on macOS systems, improves cross-platform compatibility, and simplifies file operations related to the OSX.

Key changes:

Added a new function _get_desktop_dir() to retrieve the desktop path on macOS Added the get_desktop_dir() to the StoragePath facade Added a line in the test_storagepath.py to test whether it works as intented

Please review and let me know if any further modifications are needed.