doc: add coverage to readme

README.md

@@ -5,6 +5,7 @@ Vonage Client Library for .NET
 [![Build Status](https://github.com/Vonage/vonage-dotnet-sdk/actions/workflows/net-build.yml/badge.svg)](https://github.com/Vonage/vonage-dotnet-sdk/actions/workflows/net-build.yml/badge.svg)
 [![MultiFramework Build Status](https://github.com/Vonage/vonage-dotnet-sdk/actions/workflows/multiframework-build.yml/badge.svg)](https://github.com/Vonage/vonage-dotnet-sdk/actions/workflows/multiframework-build.yml/badge.svg)
 [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=Vonage_vonage-dotnet-sdk&metric=alert_status)](https://sonarcloud.io/summary/new_code?id=Vonage_vonage-dotnet-sdk)
+[![Coverage](https://sonarcloud.io/api/project_badges/measure?project=Vonage_vonage-dotnet-sdk&metric=coverage)](https://sonarcloud.io/summary/new_code?id=Vonage_vonage-dotnet-sdk)
 [![CodeScene Code Health](https://codescene.io/projects/29782/status-badges/code-health)](https://codescene.io/projects/29782)
 [![Mutation testing badge](https://img.shields.io/endpoint?style=flat&url=https%3A%2F%2Fbadge-api.stryker-mutator.io%2Fgit.luolix.top%2FVonage%2Fvonage-dotnet-sdk%2FVonage%2Fmain)](https://dashboard.stryker-mutator.io/reports/github.com/Vonage/vonage-dotnet-sdk/Vonage/main)
 [![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg)](CODE_OF_CONDUCT.md)