[DOC] Extend permission list with transform cluster permissions

[stevanbz]

What do you want to do?

Add missing transform cluster permissions in permission list:
https://opensearch.org/docs/latest/security-plugin/access-control/permissions/

- cluster:admin/opendistro/transform/index
- cluster:admin/opendistro/transform/get
- cluster:admin/opendistro/transform/preview
- cluster:admin/opendistro/transform/delete
- cluster:admin/opendistro/transform/start
- cluster:admin/opendistro/transform/stop
- cluster:admin/opendistro/transform/explain