message: docs: update code sample for custom processors
  getProcessorName is mandatory
diff: @@ -377,6 +377,10 @@ import {
  export class SystemXReaderProcessor implements CatalogProcessor {
  constructor(private readonly reader: UrlReader) {}
  + getProcessorName(): string {
  + return 'SystemXReaderProcessor';
  + }
  +
  async readLocation(
  location: LocationSpec,
  _optional: boolean,
  