add links to install docs for required cli tools

Backup-and-Recovery-with-K8up.md

@@ -18,10 +18,10 @@ PR ref: https://github.com/seaweedfs/seaweedfs/pull/5034
 
 ## Requirements
 
-- Kubectl
-- Helm
-- Restic
-- S3 CLI tool of your choice, I'll be using `mc`
+- [Kubectl](https://kubernetes.io/docs/tasks/tools/)
+- [Helm](https://helm.sh/docs/intro/install/)
+- [Restic](https://restic.readthedocs.io/en/latest/020_installation.html)
+- S3 CLI tool of your choice, I'll be using [mc](https://github.com/minio/mc)
 
 <h2 id="k3s-cluster-creation">K3s Cluster creation</h2>