Add an example for cluster with AD on windows server

[aayushrangwala]

fixes #67

[ctreatma]

Linting failed in CI; could you run terraform fmt and commit/push the changes?

[aayushrangwala]

/rerun

[displague]

│ Error: Failed to install provider
│ 
│ Error while installing hashicorp/tls v4.0.5: open
│ /home/runner/.terraform.d/plugin-cache/registry.terraform.io/hashicorp/tls/4.0.5/linux_amd64/terraform-provider-tls_v4.0.5_x5:
│ text file busy

The linter CI has been very flaky.

[ctreatma]

Linting is still failing, but I think that's only tangentially related to this PR. I've run this end-to-end and confirmed that, as long as I don't get an HTTP 422 while setting up AD, my cluster ends up in the desired state.

In the future we can look at breaking down the null resource scripts into even smaller pieces and/or implementing sleeps or retries to reduce the occurrence of failed HTTP requests.