message: Add reviewers for crypto code
  Closes:
diff: +# Subscribe to crypto crate changing PRs
  +/crypto @kchalkias @huitseeker @valerini
  # Subscribe to potential JSON API changing PRs
  /json-rpc/json-rpc-spec.md @thefallentree @xli
  /json-rpc/types/ @thefallentree @xli
  