RELEASE.md

Release checklist

1. Update the version in each Cargo.toml.
2. Update versions in src/new.rs for stdlib etc if required.
3. Run make test build.
4. Update CHANGELOG.md with new version and link to blog post (if present)
5. Git commit, tag, push, push tags.
6. Wait for CI release build to finish.
7. Publish release on GitHub from draft made by CI.
8. Update version in Cargo.toml to next-dev.
9. Update clone target version in getting-started.md in website.
10. Update downloaded version in Dockerfile in example-echo-server.