Valkey release stage documentation (valkey-io#252)

This PR add info documentation about:

1. valkey_version
2. valkey_release_stage

adds documentation for: valkey-io/valkey#1724

---------

Signed-off-by: Ran Shidlansik <ranshid@amazon.com>
Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

Author: ranshid

commands/info.md

@@ -272,6 +272,8 @@ Here is the description of fields.
 Here is the meaning of all fields in the **server** section:
 
 *   `redis_version`: Redis OSS version this Valkey server is compatible with
+*   `valkey_version`: Valkey version number (e.g. 7.2.5)
+*   `valkey_release_stage`: The status of the Valkey version: "ga" for generally available versions; "rc1", "rc2", etc. for release candidates; "dev" for development versions. Added in 8.1.
 *   `redis_git_sha1`:  Git SHA1
 *   `redis_git_dirty`: Git dirty flag
 *   `redis_build_id`: The build id