Multikey VerificationMethod support

Currently by my reading of the docs, i’m able to update a DIDDoc with VMs of type:

• Ed25519VerificationKey2020

• EcdsaSecp256k1VerificationKey2019

• RsaVerificationKey2018

(source) https://docs.cheqd.io/product/advanced/sdk/did-module#supported-key-types

Although the source code seems to indicate:

• JsonWebKey2020 (key types ECDSA, Ed25519 & RSA are seemingly supported)

• Ed25519VerificationKey2020

• Ed25519VerificationKey2018

(source)

https://github.com/cheqd/cheqd-node/blob/2089162a071d1a741696a256457d656fa9457968/x/did/types/diddoc_verification_method.go#L17

It would be nice if it was also possible to push Multikey VM types. Anecdotally, i’ve seen this VM grow in popularity over the years, as it is able to represent a huge range of key types with a single VM type, and is also compact. Similar properties to JsonWebKey2020, but arguably more compact and could be overtaking it in popularity.

The support for the VM could be done in the same way as JsonWebKey2020 - limited scope to ed25519, ecdsa & rsa key type support.

Supporting multikey VMs in cheqd DID Docs may improve interoperability in systems which prefer Multikey to it’s alternatives (e.g. JsonWebKey2020)