Update supported elasticache resources

[kirananil007]

Description of changes:

Updating the README for AWS ACK Elasticache with added support for resources such as serverless cache, serverless cache snapshot and cache cluster.

Please see the image snippet and the ack documentation link.
https://aws-controllers-k8s.github.io/community/reference/elasticache/v1alpha1/cachecluster/

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Thanks!

[ack-prow]

Hi @kirananil007. Thanks for your PR.

I'm waiting for a aws-controllers-k8s 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.

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[kirananil007]

/assign @a-hilaly

[a-hilaly]

Thank you @kirananil007 !
/lgtm

[ack-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: a-hilaly, kirananil007

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