[DOC] Update docs for date processor in Data Prepper

[oeyh]

What do you want to do?

• [x] Request a change to existing documentation
• [ ] Add new documentation
• [ ] Report a technical problem with the documentation
• [ ] Other

Tell us about your request. Provide a summary of the request and all versions that are affected. The existing docs are missing a few new options. This readme has the latest info: https://github.com/opensearch-project/data-prepper/blob/main/data-prepper-plugins/date-processor/README.md

What other resources are available? Provide links to related issues, POCs, steps for testing, etc. Existing doc: https://opensearch.org/docs/latest/data-prepper/pipelines/configuration/processors/date/

[Naarcha-AWS]

@oeyh: Is this and the mutate event processor specifically for Data Prepper 2.7?

[oeyh]

@Naarcha-AWS This is not for 2.7. The relevant code is released, but the docs have a gap.

Specifically, it's missing:

• Details about the patterns option under match block
• to_origination_metadata option

It's also better to have some examples.