[DOCS] Add information for setting up Elasticsearch S3 snapshot repo with custom CA

[a03nikki]

Proposal

Expand the documentation for setting up Elasticsearch snapshots to include S3.

Use case. Why is this important?

Create automated snapshots (v2.2) documentation only includes an example for Google Cloud Storage (GCS). It would be helpful if there was also an example and directions for S3 both AWS and S3-compatable services. AWS' S3 is easier to set-up because it does not involve dealing with TLS settings that S3-compable services, such as Minio and Ceph, that may use custom CAs.

There is elastic/elasticsearch#77081 to make managing the certificates easier for the repositories so users no longer need to edit the "JVM-wide trustore":

By default Elasticsearch communicates with your storage system using HTTPS, and validates the repository’s certificate chain using the JVM-wide truststore. Ensure that the JVM-wide truststore includes an entry for your repository.

However, an example and directions for using Minio (the recommended non-AWS S3 provider for ECE) or another S3-compatable service with HTTPS and certificates is still needed.