Adding RAG notebook for associated learn article (#463)

## Problem

Adding a new notebook to demonstrate RAG with hybrid search using
integrated embedding and Claude for generation, with no other external
libraries.

## Solution

Describe the approach you took. Link to any relevant bugs, issues, docs,
or other resources.

## Type of Change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update
- [ ] Infrastructure change (CI configs, etc)
- [ ] Non-code change (docs, etc)
- [ ] None of the above: (explain here)

## Test Plan

Describe specific steps for validating this change.

Author: jennapederson