Set publishing category (#350)

dotnet/source-build#5070

Author: ViktorHofer

eng/Publishing.props

@@ -0,0 +1,9 @@
+<Project>
+
+  <!-- Update Artifacts with Kind=Package to have additional metadata item Category="ToolingPackage".
+       Depending on channel configuration, this means that these assets could be pushed to a different feed. -->
+  <ItemGroup>
+    <Artifact Update="@(Artifact->WithMetadataValue('Kind', 'Package'))" Category="ToolingPackage" />
+  </ItemGroup>
+
+</Project>