Add neptune example notebook and documentation

[acarbonetto]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # #3155

This PR updates the following pages and examples:

• https://docs.mem0.ai/examples/aws_example#aws-bedrock-and-aoss
• https://docs.mem0.ai/open-source/graph_memory/overview#initialize-neptune-analytics
• https://github.com/mem0ai/mem0/blob/main/examples/graph-db-demo/neptune-example.ipynb

Notebooks also includes graph-explorer visualizations when using neptune.

Type of change

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• Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

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• Test Script (please provide)

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed