Add isUnion

Author: Bashamega

inputfiles/patches/wasm-js-api.kdl

@@ -1,5 +1,5 @@
 typedef Exports legacyNamespace=WebAssembly {
-  type record {
+  type record union=#true {
     type DOMString
     type ExportValue
   }

src/build/patches.ts

@@ -62,12 +62,11 @@ function handleSingleTypeNode(type: Node): DeepPartial<Typed> {
   const typeValue = type.values[0];
   const subType =
     type.children.length > 0 ? handleTyped(type.children) : undefined;
+  const isUnion = typeof type.properties.union == "boolean";
   return {
     ...optionalMember("type", "string", typeValue),
     subtype:
-      typeValue == "record" && typeof subType?.type !== "string"
-        ? subType?.type
-        : subType,
+      isUnion && typeof subType?.type !== "string" ? subType?.type : subType,
     ...optionalMember("nullable", "boolean", type.properties?.nullable),
   };
 }