Update useCustomCountFn parameter type in documentation and implement…

[AlexSmirnov9107]

🚀 Improve Pagination Count Logic & Enhance Custom Count Function
Description:
This PR introduces two improvements to the pagination logic:

Use estimatedDocumentCount() When Query Is Empty
Pagination now uses estimatedDocumentCount() when the query object is empty, and falls back to countDocuments(query) when filters are present.

✨ Pass Query to useCustomCountFn
The useCustomCountFn option now receives the current query as an (optional) parameter, allowing for more flexible custom count logic.

Reasoning & Benefits:

⚡️ Performance:
estimatedDocumentCount() is much faster for unfiltered queries, as it uses collection metadata instead of scanning documents.

🔍 Accuracy:
For filtered queries, countDocuments(query) ensures the count matches the filter criteria.

🛠️ Extensibility:
Passing the query to useCustomCountFn enables advanced custom count scenarios that depend on the current query context.

📚 Best Practices:
Aligns with MongoDB recommendations for counting documents and improves documentation/type annotations.

🛡️ Backward Compatibility:
Existing behavior is preserved for filtered queries and for custom count functions that do not use the new parameter.

Summary of Changes:

🚄 Use estimatedDocumentCount() for empty queries to improve performance.
📝 Pass query as an (optional) parameter to useCustomCountFn.
📚 Update JSDoc/type annotations to reflect the new behavior.
No breaking changes:
If your custom count function does not use the new parameter, it will continue to work as before. 👍

[aravindnc]

@AlexSmirnov9107 Thanks. Can you please add a test case for this too.