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/ImageHandling/ImageFormats.cs

@@ -0,0 +1,40 @@
+using ClosedXML.Excel;
+using ClosedXML.Excel.Drawings;
+using System.IO;
+using System.Reflection;
+
+namespace ClosedXML_Examples
+{
+    public class ImageFormats : IXLExample
+    {
+        public void Create(string filePath)
+        {
+            var wb = new XLWorkbook();
+            IXLWorksheet ws;
+
+            using (Stream fs = Assembly.GetExecutingAssembly().GetManifestResourceStream("ClosedXML_Examples.Resources.ImageHandling.jpg"))
+            {
+                #region Jpeg
+
+                ws = wb.Worksheets.Add("Jpg");
+                ws.AddPicture(fs, XLPictureFormat.Jpeg, "JpegImage")
+                    .MoveTo(ws.Cell(1, 1));
+
+                #endregion Jpeg
+            }
+
+            using (Stream fs = Assembly.GetExecutingAssembly().GetManifestResourceStream("ClosedXML_Examples.Resources.ImageHandling.png"))
+            {
+                #region Png
+
+                ws = wb.Worksheets.Add("Png");
+                ws.AddPicture(fs, XLPictureFormat.Png, "PngImage")
+                    .MoveTo(ws.Cell(1, 1));
+
+                #endregion Png
+
+                wb.SaveAs(filePath);
+            }
+        }
+    }
+}