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/Columns/ColumnSettings.cs

@@ -0,0 +1,80 @@
+using System;
+using ClosedXML.Excel;
+
+
+namespace ClosedXML_Examples.Columns
+{
+    public class ColumnSettings : IXLExample
+    {
+        #region Variables
+
+        // Public
+
+        // Private
+
+
+        #endregion
+
+        #region Properties
+
+        // Public
+
+        // Private
+
+        // Override
+
+
+        #endregion
+
+        #region Constructors
+
+        // Public
+        public ColumnSettings()
+        {
+
+        }
+
+
+        // Private
+
+
+        #endregion
+
+        #region Events
+
+        // Public
+
+        // Private
+
+        // Override
+
+
+        #endregion
+
+        #region Methods
+
+        // Public
+        public void Create(String filePath)
+        {
+            var workbook = new XLWorkbook();
+            var ws = workbook.Worksheets.Add("Column Settings");
+
+            var col1 = ws.Column("B");
+            col1.Style.Fill.BackgroundColor = XLColor.Red;
+            col1.Width = 20;
+
+            var col2 = ws.Column(4);
+            col2.Style.Fill.BackgroundColor = XLColor.DarkOrange;
+            col2.Width = 5;
+
+            workbook.SaveAs(filePath);
+        }
+
+        // Private
+
+        // Override
+
+
+        #endregion
+    }
+}