Add documentation for the MongoDB Atlas Vector Store

[tzolov]

Consider extending the existing WIP: https://github.com/spring-projects/spring-ai/blob/main/spring-ai-docs/src/main/antora/modules/ROOT/pages/api/vectordbs/mongodb.adoc

[ThomasVitale]

Did #962 fixed this issue?

[markpollack]

The prerequisite section is missing. See https://docs.spring.io/spring-ai/reference/api/vectordbs/pinecone.html#_prerequisites for an example of hosted model docs. Reaching out to mongodb contacts to see if they want to contribute.

[ashni-mehta]

Hi all, pending changes have been submitted in a PR here: #1181. Thank you!