add Redis to list

Author: cephalin

.devcontainer/README.md

@@ -6,4 +6,5 @@ The dev container configuration lets you open the repository in a [GitHub codesp
 
 - Python
 - PostgreSQL
+- Redis
 - [Azure Developer CLI](https://learn.microsoft.com/azure/developer/azure-developer-cli/overview) (so you can run `azd` commands directly).