ci: add action for shellcheck linter

we are adding new linter for shellcheck.
As we are writing more shell scripts this
will help maintain quality.

Also, doing all the changes required in
bash files to pass this shellcheck.

Closes: https://github.com/rook/rook/issues/8431
Signed-off-by: subhamkrai <srai@redhat.com>

tests/scripts/webhook-patch-ca-bundle.sh

@@ -5,7 +5,8 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
-export CA_BUNDLE=$(kubectl get configmap -n kube-system extension-apiserver-authentication -o=jsonpath='{.data.client-ca-file}' | base64 | tr -d '\n')
+CA_BUNDLE=$(kubectl get configmap -n kube-system extension-apiserver-authentication -o=jsonpath='{.data.client-ca-file}' | base64 | tr -d '\n')
+export CA_BUNDLE
 
 if command -v envsubst >/dev/null 2>&1; then
     envsubst