Add Enum supports

Author: hi-xiaoxin

src/SourceGeneration.Reflection/SourceReflectionAttribute.cs

@@ -1,4 +1,4 @@
 namespace SourceGeneration.Reflection;
 
-[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum)]
 public class SourceReflectionAttribute : Attribute { }