Adjust examples to show relations for `members` and clarify hgvs expressions

[brendanreardon]

Feature description

We should adjust examples to do the following:

• Update expressions of underlying VRS Alleles to only include expressions of the actual Allele represented, not liftovers or translations; e.g., if the VRS Allele is an hgvs.g, don't show hgvs.c and hgvs.p. These can still be included in members. Inspired from this Pull Request comment.
• Include an extension for all members to show how they relate to the case CategoricalVariant. Inspired from this Discussion comment.

Contribution

Yes, I can create a PR for this feature.