Try adding a nuspec file

wixext/WixBalExtensionExt.csproj

@@ -77,6 +77,9 @@
       <Link>Data\balExt.wixlib</Link>
     </EmbeddedResource>
   </ItemGroup>
+  <ItemGroup>
+    <None Include="WixBalExtensionExt.nuspec" />
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

wixext/WixBalExtensionExt.nuspec

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
+    <metadata>
+        <!-- Required elements-->
+        <id>WixBalExtensionExt</id>
+        <version></version>
+        <description></description>
+        <authors>Chris Kaczor</authors>
+    </metadata>
+</package>