Update badges in README with GitHub Actions CI.

README.md

@@ -13,9 +13,9 @@ rich declaration and type information model.
 
 ## Releases/Build Status
 
-|Windows 64-bit|Windows 32-bit| windows-vs-x86            | linux-gcc-x86_64            | osx-clang-x86               |
-|---------------------------|---------------------------|---------------------------|-----------------------------|-----------------------------|
-| [![NuGet](https://img.shields.io/nuget/v/CppSharp.svg)](https://www.nuget.org/packages/CppSharp/) | [![GitHub release](https://img.shields.io/github/release/mono/CppSharp.svg)](https://github.com/mono/CppSharp/releases) | [![windows-vs-x86](https://ci.appveyor.com/api/projects/status/5o9gxjcttuaup671/branch/master?svg=true)](https://ci.appveyor.com/project/tritao/CppSharp/branch/master) | [![linux-gcc-x86_64](https://travis-ci.org/mono/CppSharp.svg?branch=master)](https://travis-ci.org/mono/CppSharp) | [![osx-clang-x86](https://travis-ci.org/mono/CppSharp.svg?branch=master)](https://travis-ci.org/mono/CppSharp)
+| NuGet Packages            | GitHub Releases           | Continuous Integration    |
+|---------------------------|---------------------------|---------------------------|
+| [![NuGet](https://img.shields.io/nuget/v/CppSharp.svg)](https://www.nuget.org/packages/CppSharp/) | [![GitHub release](https://img.shields.io/github/release/mono/CppSharp.svg)](https://github.com/mono/CppSharp/releases) | [![GitHub-actions](https://github.com/mono/CppSharp/workflows/CI/badge.svg)](https://github.com/mono/CppSharp/actions?query=workflow%3ACI) 
 
 1. [Libraries](#libraries)
 2. [Documentation](#documentation)