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/Styles/StyleRowsColumns.cs

@@ -0,0 +1,34 @@
+using System;
+using ClosedXML.Excel;
+
+
+namespace ClosedXML_Examples.Styles
+{
+    public class StyleRowsColumns : IXLExample
+    {
+        public void Create(String filePath)
+        {
+            var workbook = new XLWorkbook();
+            var ws = workbook.Worksheets.Add("Style Rows and Columns");
+
+            //Set the entire worksheet's cells to be bold and with a light cyan background
+            ws.Style.Font.Bold = true;
+            ws.Style.Fill.BackgroundColor = XLColor.LightCyan;
+
+            // Set the width of all columns in the worksheet
+            ws.Columns().Width = 5;
+
+            // Set the height of all rows in the worksheet
+            ws.Rows().Height = 20;
+
+            // Let's play with the rows and columns
+            ws.Rows(2, 3).Style.Fill.BackgroundColor = XLColor.Blue;
+            ws.Columns(3, 4).Style.Fill.BackgroundColor = XLColor.Orange;
+            ws.Rows(5, 5).Style.Fill.BackgroundColor = XLColor.Pink;
+            ws.Row(6).Style.Fill.BackgroundColor = XLColor.Brown;
+            ws.Column("E").Style.Fill.BackgroundColor = XLColor.Gray;
+
+            workbook.SaveAs(filePath);
+        }
+    }
+}