Update index.d.ts type IOsTypes

[TakuyaTaniguchi]

Hi

Introduction: First, thank you for creating this excellent library. It has been incredibly beneficial for our project.

Summary: This PR introduces strict string types to IOsTypes in the index.d.ts file. The changes ensure more precise type checking for better code reliability and maintainability. The update modifies five lines to implement these strict types, which enhances the type safety in the codebase.

Changes:

Add strict string types to IOsTypes definitions. Improve type precision and validation. Purpose: To enhance the accuracy and reliability of type checking in the project by enforcing strict string types.