Set org.opencontainers.image.description

[Vincinator]

What would you like to be added:
Set org.opencontainers.image.description annotation with basic description.

• include List of features used for this image
• include architecture
• include image filetype and archive filetype
• maybe more

everything in the description is aimed only for human readability, no further processing of this information as all the information required for automating is already provided in other labels and media_types

Why is this needed:
So that the github packages interface shows the description.
(example of what is shown when no description is provided: https://github.com/gardenlinux/repo-debian-snapshot/pkgs/container/repo-debian-snapshot/260515835?tag=1724141433)

[eigenpaul]

First iteration of this is now merged with gardenlinux/python-gardenlinux-lib#81
https://github.com/gardenlinux/python-gardenlinux-lib/blob/95772b9a6d91e96acb1462182bb69058ca421a31/src/python_gardenlinux_lib/oras/registry.py#L565-L572
How it looks on ghcr.io