Release Process (#2490)

Writing down the processes to do our releases.

Status: please review & approve so we can go ahead.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com>

README.md

@@ -35,6 +35,26 @@ Polkadot.
 
 Cumulus is a set of tools for writing Substrate-based Polkadot parachains.
 
+## Releases
+
+> [!NOTE]  
+> Our release process is still Work-In-Progress and may not yet reflect the aspired outline here.
+
+The Polkadot-SDK has two release channels: `stable` and `nightly`. Production software is advised to only use `stable`.
+`nightly` is meant for tinkerers to try out the latest features. The detailed release process is described in
+[RELEASE.md](docs/RELEASE.md).
+
+### Stable
+
+`stable` releases have a support duration of **three months**. In this period, the release will not have any breaking
+changes. It will receive bug fixes, security fixes, performance fixes and new non-breaking features on a **two week**
+cadence.
+
+### Nightly
+
+`nightly` releases are released every night from the `master` branch, potentially with breaking changes. They have
+pre-release version numbers in the format `major.0.0-nightlyYYMMDD`.
+
 ## Upstream Dependencies
 
 Below are the primary upstream dependencies utilized in this project: