message: add link to local README.md
diff: @@ -3,6 +3,7 @@ name = "cardano"
  version = "0.1.0"
  authors = ["Vincent Hanquez <vincent.hanquez@iohk.io>", "Nicolas Di Prima <nicolas.diprima@iohk.io>", "The Rust-Crypto Project Developers"]
  license = "MIT OR Apache-2.0"
  +readme = "README.md"
  repository = "https://github.com/input-output-hk/rust-cardano"
  homepage = "https://github.com/input-output-hk/rust-cardano/cardano#README.md"
  description = """
  