Add release notes for v0.58 mirroring (#4660)

* Add release notes for v0.58

Author: codebien

Diff for: release notes/v0.58.0.md

@@ -0,0 +1,8 @@
+The `v0.58.0` release mirrors the previous `v1.0.0-rc1` release to allow automation tools to recognize it as the latest version.
+For example, Homebrew's k6 formulae and pkg.go.dev do not automatically fetch unstable versions such as `v1.0.0-rc1`, which is legitimately the expected behavior for these tools.
+
+However, this has been the default for all previous `v0.*` releases, where they were considered the latest stable version—even if they were under a version typically associated with unstable releases. To address this, we will continue releasing mirrored versions under `v0.*` for necessary release candidates.
+
+This practice will end once the official stable `v1.0.0` release is available, after which we will follow the standard SemVer lifecycle to simplify the workflow for everyone.
+
+The release notes for [v1.0.0-rc1](https://github.com/grafana/k6/releases/v1.0.0-rc1) provide a detailed look at all the changes that have been implemented since `v0.57.0` and are now part of this version.