Added Microsoft.NET.Test.Sdk package reference

Author: Necas209

DotNetExtensions.slnx

@@ -1,4 +1,4 @@
 <Solution>
-    <Project Path="DotNetExtensions\DotNetExtensions.csproj" Type="Classic C#"/>
-    <Project Path="DotNetExtensionsTests\DotNetExtensionsTests.csproj" Type="Classic C#"/>
+    <Project Path="DotNetExtensions\DotNetExtensions.csproj" Type="C#" />
+    <Project Path="DotNetExtensionsTests\DotNetExtensionsTests.csproj" Type="C#" />
 </Solution>

DotNetExtensions/DotNetExtensions.csproj

@@ -13,7 +13,7 @@
     </PropertyGroup>
 
     <PropertyGroup>
-        <Version>5.8.0</Version>
+        <Version>5.8.1</Version>
         <Authors>Diogo Medeiros</Authors>
         <Company>Diogo Medeiros</Company>
         <Description>This is a collection of extension methods for .NET Core.</Description>

DotNetExtensionsTests/DotNetExtensionsTests.csproj

@@ -17,4 +17,8 @@
         <ProjectReference Include="..\DotNetExtensions\DotNetExtensions.csproj"/>
     </ItemGroup>
 
+    <ItemGroup>
+      <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
+    </ItemGroup>
+
 </Project>