README.md

ECDSA example

This is a copy-of-paste of the code in RISC0 example repo, for the pure purpose of changing the dependencies.

https://github.com/risc0/risc0/blob/main/examples/ecdsa/methods/guest/src/bin/ecdsa_verify.rs

We may make additional edits to test larger quantity of ECDSA signature verification.