Add basic metadata to custom TAFs (Series/Episode/ImageURL)

[SciLor]

The TAF-Header has 4096 bytes of usable data, only a fraction is used currently. So there is space to add some basic metadata.

This is already done for encoding purposes: https://github.com/toniebox-reverse-engineering/teddycloud/blob/master/proto/toniebox.pb.taf-header.proto