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/PageSetup/Sheets.cs

@@ -0,0 +1,34 @@
+using System;
+using ClosedXML.Excel;
+
+
+namespace ClosedXML_Examples.PageSetup
+{
+    public class Sheets : IXLExample
+    {
+        #region Methods
+
+        // Public
+        public void Create(String filePath)
+        {
+            var workbook = new XLWorkbook();
+            var ws1 = workbook.Worksheets.Add("Separate PrintAreas");
+            ws1.PageSetup.PrintAreas.Add("A1:B2");
+            ws1.PageSetup.PrintAreas.Add("D3:D5");
+
+            var ws2 = workbook.Worksheets.Add("Page Breaks");
+            ws2.PageSetup.PrintAreas.Add("A1:D5");
+            ws2.PageSetup.AddHorizontalPageBreak(2);
+            ws2.PageSetup.AddVerticalPageBreak(2);
+            
+            workbook.SaveAs(filePath);
+        }
+
+        // Private
+
+        // Override
+
+
+        #endregion
+    }
+}