[DOC] Add conversation search feature

[ylwu-amzn]

What do you want to do?

• 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.
Community developer contributes a new conversation search feature opensearch-project/ml-commons#1150. Plan to release in 2.10 for now.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

[austintlee]

@Naarcha-AWS is there anything we need to meet the RC criteria?

[Naarcha-AWS]

Hey @austintlee! Excited for this feature. In order to meet the RC criteria, we need:

1. A draft of the initial documentation, written by you, in markdown. This makes the tech review process easier since I don't have to source technical specifics on the Conversation API myself. You can submit the draft either as a PR or through this issue.
2. After I receive a draft from you, I can go ahead and edit the draft, which includes testing, grammar, and asking any clarifying questions I might have. Once the draft is in a place we're both happy with, we'll pass it along through the documentation review process.

Feel free to reach out to me if you have any more questions.

[Naarcha-AWS]

@austintlee: We're going to release the first RC tonight at 5 PM PDT. Any content you can provide would be helpful!

[HenryL27]

Conversation Feature Docs.md
Here's some documentation for the memory api and roughly the pipeline part. I'll add the pipeline sections next

[HenryL27]

RAG Search Pipeline Docs.md
Here's the Pipeline section. LMK if there's anything else I can give you