Add a new draft to help with the release

RELEASE.md

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+## Tips on making a new release for MirageOS
+
+This document aims to streamline the release process for
+MirageOS. It's a living document, evolving with each
+release. Contributions to enhance this guide are highly encouraged!
+
+## Before the release
+
+- Check that `let min = "xxx" and max = "yyy" in` `lib/mirage.ml`
+  is a range that contains the new release number.
+- Rename `## Unreleased` to `## vXXX (YYY-MM-DD)` in CHANGES.md. Open a
+  Pull Request (PR) with these changes to begin the release process.
+
+and open a PR
+
+### Release `mirage` and `mirage-runtime` to opam-repository
+
+- Tag with `dune-release tag`
+- Release to opam-repository with `dune-release`
+- Backport packaging fixes in the repo (usually lower-bounds).
+  Ideally this should be done before submitting to opam-repository but
+  right now it's not super convenient to do so.
+
+### Update `mirage-skeleton`
+
+- Verify that all changes in the main branch are correctly ported to
+  the dev branch and vice versa. This step ensures that both branches
+  reflect the latest, stable changes.
+- When complete, force-push dev to become the new main, solidifying
+  these updates.
+
+### Update `mirage-www`
+
+- Confirm that the MirageOS website builds successfully with the newly
+  released version. To facilitate this, update the `mirageio.opam.template`
+  pins to test against the new version ahead of the official release.