FcsBTreeN.BtnAddFirst(), new examples

Author: inmem

README.md

@@ -19,6 +19,7 @@ A library of cross platform C# data structures. Generic [**B-tree**](https://en.
 ### Examples
 * [BtnEnumerator.Core.examples](BtnEnumerator.Core.examples), [BtnEnumerator.NET.examples](BtnEnumerator.NET.examples)
 * [FcsFastBTreeN.Core.benchmark](FcsFastBTreeN.Core.benchmark), [FcsFastBTreeN.NET.benchmark](FcsFastBTreeN.NET.benchmark)
+* [MultipleKeys.Core.examples](MultipleKeys.Core.examples), [MultipleKeys.NET.examples](MultipleKeys.NET.examples)
 
 ### Performance
 A [**B-tree**](https://en.wikipedia.org/wiki/B-tree) of order m is a tree which satisfies the following properties: