Add MemoryPack issue

Author: Metalnem

README.md

@@ -98,6 +98,7 @@ request for the README file, or file an issue.
 - [Markdig: Markdown.ToHtml throws NullReferenceException](https://github.com/lunet-io/markdig/issues/277) **fixed**
 - [Markdig: StackOverflowException is throw when converting special markdown to HTML](https://github.com/xoofx/markdig/issues/497) **fixed**
 - [MarkdownSharp: Markdown.Transform hangs permanently](https://github.com/StackExchange/MarkdownSharp/issues/8)
+- [MemoryPack: AcessViolationException from MemoryPackReader.ReadString](https://github.com/Cysharp/MemoryPack/issues/306)
 - [MessagePack for C#: MessagePackSerializer.Deserialize<dynamic> hangs permanently](https://github.com/neuecc/MessagePack-CSharp/issues/359) **fixed**
 - [MessagePack for CLI: Unpacking.UnpackObject throws several unexpected exceptions](https://github.com/msgpack/msgpack-cli/issues/311)
 - [Mono.Cecil: ModuleDefinition.ReadModule can throw many (possibly) unexpected exceptions](https://github.com/jbevain/cecil/issues/556)