[FEATURE] Add example for ingesting documents into nested (child) topics

[virginia-delos]

Problem Statement

The guide demonstrates how to create nested topics, but does not provide an example of how to ingest documents into a child topic.

Proposed Solution

Add an example showing how to ingest documents into a nested topic using the correct topic path format. For example:

python manage.py ingest "parentTopic/childTopic" ./data/parentTopic/childTopic/*.pdf

Also include a short explanation clarifying how parent and child topic paths should be referenced during ingestion.

Alternative Solutions

Provide a complete workflow example that includes creating a parent topic, creating a child topic, placing documents, and ingesting them.

Use Case

A user creates a nested topic (e.g., tutorials under documentation) but is unsure how to ingest documents into that child topic. Without an example, they may incorrectly format the topic path or encounter errors.