Update README.md

Author: nikitasavinov

README.md

@@ -3,6 +3,7 @@
 Please refer to EntityFrameworkCore.Extensions.Samples for usage examples
 
 # Build status
+![.NET Core](https://github.com/nikitasavinov/EntityFrameworkCore.Extensions/workflows/.NET%20Core/badge.svg)
 [![Codacy Badge](https://api.codacy.com/project/badge/Grade/24d129322030411ba52247aa7c9b0bbf)](https://app.codacy.com/app/nikitasavinov/EntityFrameworkCore.Extensions?utm_source=github.com&utm_medium=referral&utm_content=nikitasavinov/EntityFrameworkCore.Extensions&utm_campaign=Badge_Grade_Dashboard)
 [![NugetPackage](https://buildstats.info/nuget/EntityFrameworkCore.Extensions)](https://www.nuget.org/packages/EntityFrameworkCore.Extensions)