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/Misc/FreezePanes.cs

@@ -0,0 +1,36 @@
+using ClosedXML.Excel;
+using System;
+
+namespace ClosedXML_Examples.Misc
+{
+    public class FreezePanes : IXLExample
+    {
+        public void Create(String filePath)
+        {
+            using (var wb = new XLWorkbook())
+            {
+                // Freeze rows and columns in one shot
+                var ws1 = wb.AddWorksheet("Freeze1");
+                ws1.Cell(5, 5).SetActive();
+                ws1.SheetView.Freeze(3, 3);
+
+                // You can also be more specific on what you want to freeze
+                // For example:
+                var ws2 = wb.AddWorksheet("FreezeRows");
+                ws2.Cell(5, 5).SetActive();
+                ws2.SheetView.FreezeRows(3);
+
+                var ws3 = wb.AddWorksheet("FreezeColumns");
+                ws3.Cell(5, 5).SetActive();
+                ws3.SheetView.FreezeColumns(3);
+
+                var wsSplit = wb.AddWorksheet("Split View");
+                wsSplit.Cell(2, 2).SetActive();
+                wsSplit.SheetView.SplitRow = 3;
+                wsSplit.SheetView.SplitColumn = 3;
+
+                wb.SaveAs(filePath);
+            }
+        }
+    }
+}