xml docs and input parameter's nullability fix

[DeadUnicorn1352]

Description

This pr fixes a constructor parameter "filter" of GridifyQuery. It is 'string' even though property is 'string?' in nullable context passing null creates a warning (and is in general confusing), but passing empty string will fail QueryBuilder.BuildEvaluator().

Also some XML documentation had issues which in term broke documentation in rider, also fixed that.

I haven't created an issue for that

Type of change

• xml documentation and parameter nullability

[what-the-diff]

PR Summary

• Correction to XML Documentation in GridifyExtensions.cs

  • XML Documentation comments have been updated to correct the syntax for generic placeholders. This corrects the way types are presented and makes the documentation clearer and more accurate.

• Change to GridifyQuery Constructor in GridifyQuery.cs

  • Modification has been made to the GridifyQuery constructor to accept a nullable string for the filter parameter. This change enhances how inputs are handled, providing more flexibility when declaring the filter parameter.

[alirezanet]

LGTM 👌💐