[Enhancement]: Add rag-api documentation for helm chart

[KaganCansiz]

What features would you like to see added?

rag-api helm chart needs some documentation.

More details

1. When i try to deploy librechat helm chart with librechat-rag-api.enabled=true and librechat-rag-api.embeddingsProvider: openai it is not deploying. postgresql stuck on imagepullbackoff. Editing its image name and then it pops up with some env variables needed.
2. i set librechat-rag-api.enabled to false and deployed librechat-rag-api helm chart on my own which there was no documentation for rag-api helm chart.
3. could not be able to set postgresql.enabled=false. if there is no option to disable it, then there should not be an option.
4. it would be great if we can use an existing postgresql for rag-api

Which components are impacted by your request?

Plugins

Pictures

No response

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