Add link to Google.Protobuf nuget

Author: Havret

README.md

@@ -3,7 +3,7 @@
 [![Build](https://github.com/Havret/Protobuf.System.Text.Json/actions/workflows/build.yml/badge.svg)](https://github.com/Havret/Protobuf.System.Text.Json/actions/workflows/build.yml)
 [![NuGet](https://img.shields.io/nuget/vpre/Protobuf.System.Text.Json.svg)](https://www.nuget.org/packages/Protobuf.System.Text.Json/)
 
-This library provides support for Protobuf types to [System.Text.Json](https://www.nuget.org/packages/System.Text.Json/).
+This library provides support for [Google.Protobuf](https://www.nuget.org/packages/Google.Protobuf) types to [System.Text.Json](https://www.nuget.org/packages/System.Text.Json/).
 
 ## Performance