Adding nuget/myget badges (open-telemetry#913)

* Adding nuget/myget badges

* updating label from myget

* updating label again

* Update README.md

Co-authored-by: Cijo Thomas <[email protected]>

Author: eddynaka

README.md

@@ -5,6 +5,7 @@ chat](https://badges.gitter.im/open-telemetry/opentelemetry-dotnet.svg)](https:/
 [![Build
 Status](https://action-badges.now.sh/open-telemetry/opentelemetry-dotnet)](https://github.com/open-telemetry/opentelemetry-dotnet/actions)
 [![Release](https://img.shields.io/github/v/release/open-telemetry/opentelemetry-dotnet?include_prereleases&style=)](https://github.com/open-telemetry/opentelemetry-dotnet/releases/)
+[![Nuget](https://img.shields.io/nuget/vpre/OpenTelemetry.svg)](https://www.nuget.org/profiles/OpenTelemetry)
 
 The .NET [OpenTelemetry](https://opentelemetry.io/) client.