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/Ranges/SelectingRanges.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Linq;
+using ClosedXML.Excel;
+
+
+namespace ClosedXML_Examples.Ranges
+{
+    public class SelectingRanges : IXLExample
+    {
+        public void Create(String filePath)
+        {
+            var wb = new XLWorkbook();
+            var wsActiveCell = wb.AddWorksheet("Set Active Cell");
+            wsActiveCell.Cell("B2").SetActive();
+
+            var wsSelectRowsColumns = wb.AddWorksheet("Select Rows and Columns");
+            wsSelectRowsColumns.Rows("2, 4-5").Select();
+            wsSelectRowsColumns.Columns("2, 4-5").Select();
+
+            var wsSelectMisc = wb.AddWorksheet("Select Misc");
+            wsSelectMisc.Cell("B2").Select();
+            wsSelectMisc.Range("D2:E2").Select();
+            wsSelectMisc.Ranges("C3, D4:E5").Select();
+
+            wb.SaveAs(filePath);
+        }
+
+    }
+}