Add localized strings and icons for artifact types

[SteveLasker]

Capture how artifact authors can provide localized strings and logos for how their artifact can be visualized in registry specific tooling.
This surfaces the details captured here: https://github.com/opencontainers/artifacts/blob/f9710ad60b6de311843df88d8f8fa1e6d0d44b50/authoring-artifacts.md#optional-publishing-the-artifact-type

This is a dupe of OCI Artifacts/Add localized strings and icons for artifact types #45

We can either create the schema and spec here and submit as a proven PR to OCI Artifacts, or track under OCI Artifacts. Either way, we'll need this for ORAS Artifacts for authors to identify their types.

[lachie83]

Discussed at 9/8 meeting and decided to punt to draft.2