Divide release tags according to release stage (#52)

Signed-off-by: Ran Shidlansik <ranshid@amazon.com>
Signed-off-by: ranshid <ranshid@amazon.com>
Co-authored-by: Roshan Khatri <117414976+roshkhatri@users.noreply.github.com>

dockerhub-description.md

@@ -7,15 +7,25 @@
 	Please open an Issue stating your question on [the Valkey Community](https://github.com/valkey-io/valkey-container/issues).
 
 # Supported tags and respective `Dockerfile` links
-- [`unstable`, `unstable-bookworm`](https://github.com/valkey-io/valkey-container/blob/master/unstable/debian/Dockerfile)
-- [`unstable-alpine`, `unstable-alpine3.21`](https://github.com/valkey-io/valkey-container/blob/master/unstable/alpine/Dockerfile)
+
+## Official releases
+
 - [`8.0.2`, `8.0`, `8`, `latest`, `8.0.2-bookworm`, `8.0-bookworm`, `8-bookworm`, `bookworm`](https://github.com/valkey-io/valkey-container/blob/master/8.0/debian/Dockerfile)
 - [`8.0.2-alpine`, `8.0-alpine`, `8-alpine`, `alpine`, `8.0.2-alpine3.21`, `8.0-alpine3.21`, `8-alpine3.21`, `alpine3.21`](https://github.com/valkey-io/valkey-container/blob/master/8.0/alpine/Dockerfile)
 - [`7.2.8`, `7.2`, `7`, `7.2.8-bookworm`, `7.2-bookworm`, `7-bookworm`](https://github.com/valkey-io/valkey-container/blob/master/7.2/debian/Dockerfile)
 - [`7.2.8-alpine`, `7.2-alpine`, `7-alpine`, `7.2.8-alpine3.21`, `7.2-alpine3.21`, `7-alpine3.21`](https://github.com/valkey-io/valkey-container/blob/master/7.2/alpine/Dockerfile)
+
+## Release candidates
+
 - [`8.1-alpine`, `8.1.0-rc1-alpine`, `8.1.0-rc1-alpine3.21`, `8.1-alpine3.21`](https://github.com/valkey-io/valkey-container/blob/master/8.1/alpine/Dockerfile)
 - [`8.1.0-rc1`, `8.1`, `8.1.0-rc1-bookworm`, `8.1-bookworm`](https://github.com/valkey-io/valkey-container/blob/master/8.1/debian/Dockerfile)
 
+## Latest unstable
+
+- [`unstable`, `unstable-bookworm`](https://github.com/valkey-io/valkey-container/blob/master/unstable/debian/Dockerfile)
+- [`unstable-alpine`, `unstable-alpine3.21`](https://github.com/valkey-io/valkey-container/blob/master/unstable/alpine/Dockerfile)
+
+
 What is [Valkey](https://github.com/valkey-io/valkey)?
 --------------
 Valkey is a high-performance data structure server that primarily serves key/value workloads.