doc: Added link to Valkey Slack

Fixes #133

Signed-off-by: Mikhail Koviazin <[email protected]>

Author: Mikhail Koviazin

docs/index.rst

@@ -83,6 +83,7 @@ Contributing
 - `Issue Tracker <https://github.com/valkey-io/valkey-py/issues>`_
 - `Source Code <https://github.com/valkey-io/valkey-py/>`_
 - `Release History <https://github.com/valkey-io/valkey-py/releases/>`_
+- `Valkey Slack <https://valkey.io/slack/>`_
 
 License
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