chore(csproj): upgrade xunit and include dotnet watch

Author: jaredcnance

build/dependencies.props

@@ -5,7 +5,7 @@
   </PropertyGroup>
   <PropertyGroup>
     <MoqVersion>4.7.10</MoqVersion>
-    <xUnitVersion>2.2.0</xUnitVersion>
+    <xUnitVersion>2.3.1</xUnitVersion>
     <BogusVersion>8.0.1-beta-1</BogusVersion>
   </PropertyGroup>
 </Project>

test/JsonApiDotNetCoreExampleTests/JsonApiDotNetCoreExampleTests.csproj

@@ -30,5 +30,9 @@
     <PackageReference Include="Microsoft.DotNet.InternalAbstractions" Version="1.0.0" />
     <PackageReference Include="Moq" Version="$(MoqVersion)" />
   </ItemGroup>
-
+  
+  <ItemGroup>
+    <DotNetCliToolReference Include="dotnet-xunit" Version="$(XUnitVersion)" />
+    <DotNetCliToolReference Include="Microsoft.DotNet.Watcher.Tools" Version="1.0.0" />
+  </ItemGroup>
 </Project>