Update release instructions

Author: polytypic

README.md

@@ -2243,5 +2243,7 @@ OCaml) and [prettier](https://prettier.io/) (for Markdown).
 
 1. Update [CHANGES.md](CHANGES.md).
 2. Run `dune-release tag VERSION` to create a tag for the new `VERSION`.
-3. Run `dune-release` to publish the new `VERSION`.
-4. Run `./update-gh-pages-for-tag VERSION` to update the online documentation.
+3. Run `dune-release publish distrib` to create release on GitHub.
+4. Run `opam publish --tag=VERSION` to create PR to
+   [opam-repository](https://github.com/ocaml/opam-repository).
+5. Run `./update-gh-pages-for-tag VERSION` to update the online documentation.