Update _index.md

[mdstjean]

Suggest adding a disclaimer due to the age of this pattern.

Also copied the README from the pattern repo to add some content.

Please review and accept or deny. I've copied Jonny on a comment to see if this would be acceptable.

[openshift-ci]

Hi @mdstjean. Thanks for your PR.

I'm waiting for a validatedpatterns member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.