Implement the AddComment method in the Worksheet class to add or update comments in specific cells. This method ensures compatibility with existing comments, managing the worksheet's comment part and authors list dynamically. It supports adding new comments if none exist or updating existing ones, thereby enhancing the functionality of our Excel handling utility.

This update is crucial for features that rely on providing feedback or notes directly within the Excel documents, such as automated report generation or data validation processes.

- Ensure the worksheet comments part exists before adding or updating comments.
- Manage authors list to avoid duplicates and use existing indices where possible.