Doc error: OCI image manifest listed as an example of artifact manifest

[m5i-work]

An OCI image manifest is not a valid artifact manifest. But it's listed in Example ORAS Artifact Manifests (the first item).

@SteveLasker @shizhMSFT Should we reference this file instead?

[shizhMSFT]

/cc @FeynmanZhou @yizha1

[SteveLasker]

Thanks @m5i-work. This is a good clarification.
I didn't mean to imply the OCI Image is an ORAS Artifact manifest type. I just created an example for comparison, and then just listed each one.
See PR #107