message: Include changelog helper text
diff: @@ -38,6 +38,8 @@ This project follows "git flow" semantics. In practice, this means:
  `npm run check`.
  - Create a pull request. If this PR fixes an issue, link to it by referring to its number.
  - PRs from community members must be signed off as per Synapse's [Attribution section](https://github.com/matrix-org/synapse/blob/master/CONTRIBUTING.rst#attribution)
  + - Create a changelog entry in `changelog.d`. A changelog filename should be `${GithubIssueNumber}.{bugfix|misc|feature|doc|removal}`
  + The change should include information that is useful to the user rather than the developer.
  ## Coding notes
  The IRC bridge is compatible on Node.js v10+. Buildkite is used to ensure that tests will run on
  