Namespace tag docs

[bechols]

What does this PR do?

Adds tag docs to the manage namespaces page.

Tested locally.

[bechols]

Replace these inline examples with link to examples when temporalio/terraform-provider-temporalcloud#319 merges

[shivam-ajmera]

Similarly, we have a dedicated section for terraform docs here https://docs.temporal.io/production-deployment/cloud/terraform-provider#manage-temporal-cloud-namespaces-with-terraform - do we want to add there/hyperlink or better to keep the samples here?

[bechols]

Good question - the Terraform docs page is WAY out of date (for instance: it says we have 2 data sources, but we're currently close to 10) so I'm inclined to link directly to the TF repo instead.

I'll track a separate TODO to replace or update those TF docs.