Add Shreyas Londhe to SIG directory

Adding myself to the Security, Financial Workflows & Composability, Canton Protocol & Multi-Synchronizer, and Token Standards / Asset Standards SIGs.

Background: cryptography engineer focused on zero-knowledge proof systems — SNARK provers (WHIR, Spartan, Ligero-style protocols), ZK circuit security, and privacy-preserving protocol design. Recent work includes a PoPETs 2026 paper and open-source prover contributions. Interested in helping review proposals at the intersection of ZK and Canton's selective-disclosure model (e.g. the proof-of-supply-cap direction in #517) and contributing in these areas.

GitHub: shreyas-londhe · Site: https://shreyaslondhe.xyz