export the server-side base exception SmithyException from the client root

Author: AllanZhengYP

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/IndexGenerator.java

@@ -82,6 +82,9 @@ static void writeServerIndex(
         writer.write("export * from \"./operations\";");
 
         writer.write("export * from \"./$L\"", symbol.getName());
+
+        writer.write("export { SmithyException } from $S", TypeScriptDependency.SERVER_COMMON.packageName);
+
         fileManifest.writeFile(
             Paths.get(CodegenUtils.SOURCE_FOLDER, ServerSymbolVisitor.SERVER_FOLDER, "index.ts").toString(),
             writer.toString());