Add lifecycle postStart Support to Auto Populate Index Patterns into Kibana

I'd like the docs to be updated to specify that not all values listed in the original helm charts' values.yaml (https://github.com/elastic/helm-charts/blob/master/kibana/values.yaml) are supported using the bigbang helm chart. Also maybe mention that this is a standalone helm chart and that users need to refer to https://repo1.dso.mil/platform-one/big-bang/apps/core/elasticsearch-kibana/-/blob/main/chart/values.yaml for supported customization options. I think having this info in the main README would make things much easier to navigate for users of bigbang. I think this info of not being the same as the original helm chart and pointing to the correct values.yaml for all supported kustomization options would be very helpful for users of open source bigbang.

This might be obvious for someone who is used to working on helm charts / kubernetes, but it was a bit hard to figure out for me just getting started in this area and needing to set up a bigbang installation. Before diving deeper into bigbang, I'd originally thought that the bigbang helm chart was still calling the original helm chart and used the same options the original does rather than being a standalone copy.

For reference, I tried modifying the readinessProbe and lifecycle values as a test in our bigbang customer template and did not see them update.

Here are the changes I tried to put in "dev/configmap.yaml" in our copy of the bigbang customer template

logging:
  enabled: true
  values:
    kibana:
      securityContext:
        runAsUser: 0
      readinessProbe:
        failureThreshold: 10
      lifecycle:
        postStart:
          exec:
            command:
              - bash
              - -c
              - |
                #!/bin/bash -xv
                # Config the index_pattern
                TEMPLATE_NAME=default_logstash

Note that securityContext was updated since it is listed in https://repo1.dso.mil/platform-one/big-bang/apps/core/elasticsearch-kibana/-/blob/main/chart/values.yaml

EDIT: Updated title to be more accurate