feat: export PublishError (#1216)

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Fixes #1215

src/index.ts

@@ -91,6 +91,7 @@ export {
   IAM,
 } from './iam';
 export {Attributes, PublishCallback} from './publisher';
+export {PublishError} from './publisher/publish-error';
 export {
   PageOptions,
   GetSnapshotsCallback,