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/DefaultStyles.cs

@@ -0,0 +1,29 @@
+using System;
+using ClosedXML.Excel;
+
+
+namespace ClosedXML_Examples.Styles
+{
+    public class DefaultStyles : IXLExample
+    {
+        public void Create(String filePath)
+        {
+            // Create our workbook
+            var workbook = new XLWorkbook();
+
+            // This worksheet will have the default style, row height, column width, and page setup
+            var ws1 = workbook.Worksheets.Add("Default Style");
+
+            // Change the default row height for all new worksheets in this workbook
+            workbook.RowHeight = 30;
+
+            var ws2 = workbook.Worksheets.Add("Tall Rows");
+
+            // Create a worksheet and change the default row height
+            var ws3 = workbook.Worksheets.Add("Short Rows");
+            ws3.RowHeight = 7.5;
+
+            workbook.SaveAs(filePath);
+        }
+    }
+}