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/Loading/LoadFiles.cs

@@ -0,0 +1,26 @@
+using System;
+using System.IO;
+using ClosedXML.Excel;
+
+namespace ClosedXML_Examples
+{
+    public class LoadFiles
+    {
+        public static void LoadAllFiles()
+        {
+            foreach (var file in Directory.GetFiles(Program.BaseCreatedDirectory))
+            {
+                var fileInfo = new FileInfo(file);
+                var fileName = fileInfo.Name;
+                LoadAndSaveFile(Path.Combine(Program.BaseCreatedDirectory, fileName), Path.Combine(Program.BaseModifiedDirectory, fileName));
+            }
+        }
+
+        private static void LoadAndSaveFile(String input, String output)
+        {
+            var wb = new XLWorkbook(input);
+            wb.SaveAs(output);
+            wb.SaveAs(output);
+        }
+    }
+}