Add support for Synology Hyper Backup (.hbk) files

[joost-j]

Synology DSM offers the Hyper Backup application, which is able to create and restore backups.

https://www.synology.com/en-global/dsm/feature/hyper_backup

Adding Synology Hyper Backup files (.hbk) support to dissect would be a very nice addition.

[joost-j]

FYI, I started working on this a bit. Basic functionality is there, I'm currently working on adding the decryption and legacy stuff, will start a draft PR once I think it's in a decent state.