badge: Add the SIG CI failure count badge to the README

Signed-off-by: Brian Carey <[email protected]>

Author: brianmcarey

README.md

@@ -46,6 +46,7 @@ Each of these failures contribute to the number of retests that occur in CI and
 ![sig-storage-retests](https://kubevirt.io/ci-health/output/kubevirt/kubevirt/sig-storage-retests.svg)
 ![sig-network-retests](https://kubevirt.io/ci-health/output/kubevirt/kubevirt/sig-network-retests.svg)
 ![sig-operator-retests](https://kubevirt.io/ci-health/output/kubevirt/kubevirt/sig-operator-retests.svg)
+![sig-ci-retests](https://kubevirt.io/ci-health/output/kubevirt/kubevirt/sig-ci-retests.svg)
 
 Top failed lanes: