dev-docs: document microsoft containerd fork

Signed-off-by: Paul Meyer <[email protected]>

dev-docs/aks/node-image.md

@@ -4,6 +4,7 @@ Most relevant Microsoft forks for us:
 
 - https://github.com/microsoft/kata-containers
 - https://github.com/microsoft/cloud-hypervisor
+- https://github.com/microsoft/confidential-containers-containerd
 
 ## Release flow