Initial commit of the ClosedXML library

Establishes the foundational structure, core Excel functionality, and tooling.

- Implements base components for cells, ranges, columns, and rows.
- Integrates a custom calculation engine with a wide range of Excel functions.
- Adds comprehensive support for styling, conditional formatting, data validation, comments, pictures, and charts.
- Configures build setup, project metadata (NuGet), and developer guidelines.
- Includes editor and Git attributes for consistent code style and line endings.

ClosedXML_Examples/Ranges/CopyingRanges.cs

@@ -0,0 +1,37 @@
+using System.IO;
+using ClosedXML.Excel;
+
+namespace ClosedXML_Examples
+{
+    public class CopyingRanges : IXLExample
+    {
+        public void Create(string filePath)
+        {
+            var tempFile = ExampleHelper.GetTempFilePath(filePath);
+            try
+            {
+                new BasicTable().Create(tempFile);
+                var workbook = new XLWorkbook(tempFile);
+                var ws = workbook.Worksheet(1);
+
+                // Define a range with the data
+                var firstTableCell = ws.FirstCellUsed();
+                var lastTableCell = ws.LastCellUsed();
+                var rngData = ws.Range(firstTableCell.Address, lastTableCell.Address);
+
+                // Copy the table to another worksheet
+                var wsCopy = workbook.Worksheets.Add("Contacts Copy");
+                wsCopy.Cell(1, 1).Value = rngData;
+
+                workbook.SaveAs(filePath);
+            }
+            finally
+            {
+                if (File.Exists(tempFile))
+                {
+                    File.Delete(tempFile);
+                }
+            }
+        }
+    }
+}