Added release build status badge to top README

Author: smaillet

README.md

@@ -2,6 +2,7 @@
 
 Status:  
 [![CI-Build](https://github.com/UbiquityDotNET/Llvm.NET/workflows/CI-Build/badge.svg?branch=master&event=push)](https://github.com/UbiquityDotNET/Llvm.NET/actions?query=workflow%3ACI-Build+branch%3Amaster+is%3Ain_progress)
+![Release-Build](https://github.com/ubiquitydotnet/llvm.net/workflows/Release-Build/badge.svg)
 
 ### Welcome to Llvm.NET!
 Llvm.NET provides LLVM language and runtime bindings for .NET based applications. Llvm.NET's goal is to provide