add description for object storage category

- https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2984

README.md

@@ -915,6 +915,8 @@ Network distributed filesystems.
 
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+[Object storage](https://en.wikipedia.org/wiki/Object_storage) is a computer data storage that manages data as objects, as opposed to other storage architectures like file systems which manages data as a file hierarchy, and block storage which manages data as blocks within sectors and tracks.
+
 - [GarageHQ](https://garagehq.deuxfleurs.fr/) - An open-source geo-distributed storage service you can self-host to fulfill many needs - S3 compatible. ([Source Code](https://git.deuxfleurs.fr/Deuxfleurs/garage)) `AGPL-3.0` `Rust`
 - [Minio](https://minio.io/) - Minio is an open source object storage server compatible with Amazon S3 APIs. ([Source Code](https://github.com/minio/minio)) `AGPL-3.0` `Go`
 - [SeaweedFS](https://github.com/chrislusf/seaweedfs) - SeaweedFS is an open source distributed file system supporting WebDAV, S3 API, FUSE mount, HDFS, etc, optimized for lots of small files, and easy to add capacity. `Apache-2.0` `Go`