message: added additional information for s3 discovery usage
diff: @@ -26,3 +26,16 @@ catalog:
  ```
  Note the `s3-discovery` type, as this is not a regular `url` processor.
  +
  +As this processor is not one of the default providers, you will also need to add the below:
  +
  +```javascript
  +/* packages/backend/src/plugins/catalog.ts */
  +
  +import { AwsS3DiscoveryProcessor} from '@backstage/plugin-catalog-backend';
  +
  +
  +const builder = await CatalogBuilder.create(env);
  +/** ... other processors ... */
  +builder.addProcessor(new AwsS3DiscoveryProcessor(env.reader))
  +```
  