Add Pinecone Assistant sample app

[zackproser]

Problem

We have a new official sample app available for Pinecone Assistant, and we want to make it available to developers and users of our npx create-pinecone-app command.

Solution

Add a new Pinecone Assistant app.

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

This app has been tested thoroughly locally, in staging and in production.

[zackproser]

Thanks for review! Going to merge this in now.