Add Appveyor

Author: asherber

README.md

@@ -1,6 +1,6 @@
 ![Icon](https://github.com/asherber/Xunit.Priority/raw/master/media/xunit-priority-64.png)
 
-# Xunit.Priority [![NuGet](https://img.shields.io/nuget/v/Xunit.Priority.svg)](https://nuget.org/packages/Xunit.Priority)
+# Xunit.Priority [![NuGet](https://img.shields.io/nuget/v/Xunit.Priority.svg)](https://nuget.org/packages/Xunit.Priority) [![Build status](https://ci.appveyor.com/api/projects/status/h9kxm1ocxtcvf4iu/branch/master?svg=true)](https://ci.appveyor.com/project/asherber/xunit-priority/branch/master)
 
 Provides an `ITestCaseOrderer` that allows you to control the order of execution of Xunit tests within a class.
 

appveyor.yml

@@ -0,0 +1,6 @@
+version: 1.0.{build}
+image: Visual Studio 2019
+build_script:
+- cmd: dotnet build
+test_script:
+- cmd: dotnet test --no-build -v n