Update README.md

Author: Mohan2401

XlsIO.PerformanceBenchmark/README.md

@@ -1,5 +1,19 @@
-Run one method per process:
+# Performance benchmark
 
-    dotnet run -c Release -- <Method>
+`XlsIO.PerformanceBenchmark` is a .NET 9 console app that measures the elapsed time of Syncfusion XlsIO operations on a workbook with 100,000 rows by 50 columns. Each run executes one method:
 
-Methods: OpenAndSave, CreateAndSave, ImportDataTable, ExportDataTable, ExcelToCsv, ExcelToJson, ExcelToPdf
+- `OpenAndSave`
+- `CreateAndSave`
+- `ImportDataTable`
+- `ExportDataTable`
+- `ExcelToCsv`
+- `ExcelToJson`
+- `ExcelToPdf`
+
+```bash
+dotnet run --project XlsIO.PerformanceBenchmark -c Release -- ExcelToCsv
+```
+
+Generated files are written to the `Output` folder next to the built application.
+
+NuGet packages: `Syncfusion.XlsIO.Net.Core`, `Syncfusion.XlsIORenderer.Net.Core`, and `Syncfusion.Pdf.Net.Core` (35.1.41).