Fix the container image tags for v0.5 (#56)

Signed-off-by: Thibault Guittet <88336850+rh-tguittet@users.noreply.github.com>

Author: rh-tguittet

docs/downloads/index.md

@@ -9,11 +9,11 @@
     ContainerSSH can be installed in a containerized system (Kubernetes, Docker, Podman) by referencing the following image names:
 
     ```
-    containerssh/containerssh:0.5
-    containerssh/containerssh:0.5.1
+    containerssh/containerssh:v0.5
+    containerssh/containerssh:v0.5.1
 
-    quay.io/containerssh/containerssh:0.5
-    quay.io/containerssh/containerssh:0.5.1
+    quay.io/containerssh/containerssh:v0.5
+    quay.io/containerssh/containerssh:v0.5.1
     ```
 
     Our container images are built on **Alpine Linux (x86, 64 bit)**.