add vbsn method

[DuyAnhTran95]

DID Method Registration

As a DID method registrant, I have ensured that my DID method registration complies with the following statements:

• The DID Method specification defines the DID Method Syntax.
• The DID Method specification defines the Create, Read, Update, and Deactivate DID Method Operations.
• The DID Method specification contains a Security Considerations section.
• The DID Method specification contains a Privacy Considerations section.
• The JSON file I am submitting has passed all automated validation tests below.
• The JSON file contains a contactEmail address [OPTIONAL].
• The JSON file contains a verifiableDataRegistry entry [OPTIONAL].

[swcurran]

This method would meet the bar for inclusion in the registry, but the PR needs to be updated, and the "contactWebsite" is a 404. The page exists, but is "https://vbsn.vn/en/home-en".

That said, I wonder if it would be more valuable to have the spec be reduced to a list of the differences of a specific version of the did:ethr specification? Or at least add a note that highlights the differences. I had AI compare the two and they are substantially the same -- which makes sense. But it would be helpful for a reader to know the differences without comparing, and it will make it easier to evolve the spec as the did:ethr spec is updated.

I did find that did:ethr does support referencing the VBSN ledger within that method. So in theory a new DID Method is not really needed. I can guess why the method was wanted, but thought I would point that out.