Forgot to include Base.props in the last commit.

build/Base.props

@@ -1,5 +1,6 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
     <PackageReference Include="System.ValueTuple" Version="4.3.1" />
+    <PackageReference Include="System.Numerics.Vectors" Version="4.5.0-preview2-26406-04"/>
   </ItemGroup>
 </Project>