feat[manifests]: Restore root manifest

PR argoproj-labs#352 introduced the sidecar pattern, but also renamed the prior default
manifest, which was available through a reference to
https://github.com/argoproj-labs/argocd-vault-plugin//manifests

To get the same app, consumers would need to change any exsting references to
https://github.com/argoproj-labs/argocd-vault-plugin//manifests/cmp-configmap

This commit introduces a simple proxy manifest that makes that change backwards
compatible, meaning that now older references to
https://github.com/argoproj-labs/argocd-vault-plugin//manifests
will still resolve to the same app state as
https://github.com/argoproj-labs/argocd-vault-plugin//manifests/cmp-configmap
rather than just breaking.

manifests/kustomization.yaml

@@ -0,0 +1,5 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+- ./cmp-configmap