message: docs: add how to contribute title to README
diff: @@ -25,6 +25,8 @@ The wiki also lists some [known issues](https://github.com/nervosnetwork/ckb/wik
  The `master` branch is regularly built and tested, however, it is not guaranteed to be completely stable; The `develop` branch is the work branch to merge new features, and it's not stable. The CHANGELOG is available in [Releases](https://github.com/nervosnetwork/ckb/releases) and [CHANGELOG.md](https://github.com/nervosnetwork/ckb/blob/master/CHANGELOG.md) in the `master` branch.
  +## How to Contribute
  +
  The contribution workflow is described in [CONTRIBUTING.md](CONTRIBUTING.md), and security policy is described in [SECURITY.md](SECURITY.md). To propose new protocol or standard for Nervos, see [Nervos RFC](https://github.com/nervosnetwork/rfcs).
  ---
  