Create index.yaml vultisig

[realpaaao]

Adds Vultisig to the explorer: an open-source, seedless, self-custodial multi-chain
wallet that uses MPC threshold signatures (DKLS23) instead of a seed phrase.

Files:

• src/projects/vultisig/index.yaml
• src/projects/vultisig/logo.png (400x400 PNG)

Where it sits in the dataset: same category/usecase as the existing wallet entries
(edge, zengo, sparrow) — categories: [applications], usecases: [wallets, mpc],
ecosystem: [multichain].

On the privacy fields specifically, so nobody has to take my word for it:

• default_privacy is set to false. Vultisig is not a privacy protocol — no shielded
  transactions, no mixing, no Tor. connected_tx is true and dissapearing_tx is false
  for the same reason. I'd rather the entry be accurate than score well.
• What is true and checkable: no account, no e-mail, no sign-up and no KYC to use the
  wallet; the apps collect no personal data (privacy policy:
  https://vultisig.com/privacy); vault data stays on the device; the clients are
  open source under Apache-2.0 (MIT for the SDK); custody is non-custodial with
  m-of-n threshold signing, so no single party — including us — can sign alone.
• frontend_anonymity is omitted rather than filled in, because there is no built-in
  Tor or proxy support to claim.
• third_party_dependency lists the actual dependencies (RPC/price APIs, the relay
  server used for remote device pairing, and the third-party swap providers) instead
  of "none".

Audit linked is Trail of Bits' review of the DKLS23 implementation by Silence
Laboratories (2024-04-10), which is the threshold signature library the wallet uses.

Happy to adjust any field or drop ones you'd rather see left empty.

receipts

make test and make build run locally against this branch:

$ deno test -A utils/test.js
projects/vultisig [applications] (schema) ... ok (3ms)
ok | 75 passed | 0 failed (12ms)
exit=0

$ deno run -A utils/build.js
./src/projects/vultisig/logo.png -> ./dist/assets/projects/vultisig/logo.png
Bundle writed: ./dist/index.json
exit=0