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/ModifyFiles.cs

@@ -0,0 +1,14 @@
+using ClosedXML_Examples.Delete;
+using System.IO;
+
+namespace ClosedXML_Examples
+{
+    public class ModifyFiles
+    {
+        public static void Run()
+        {
+            var path = Program.BaseModifiedDirectory;
+            new DeleteRows().Create(Path.Combine(path, "DeleteRows.xlsx"));
+        }
+    }
+}