Remember to export Derivable and ProductDerivable

src/core/soundness+wisteria.scala

@@ -17,7 +17,7 @@
 package soundness
 
 export wisteria.{FieldIndex, ContextRequirement, VariantIndex, VariantError, ProductDerivation, Derivation,
-    Reflection, ProductReflection, SumReflection}
+    Reflection, ProductReflection, SumReflection, Derivable, ProductDerivable}
 
 package derivationContext:
   export wisteria.derivationContext.{required, relaxed}