Add example notebook for itinerary planning using OpenStreetMap-integration,and Haystack Agent

[grexrr]

This PR adds a tutorial notebook demonstrating how to use the OSMFetcher from osm-integration-haystack with Haystack's Agent framework.

The notebook includes:

• A pipeline that fetches nearby POIs from OpenStreetMap and summarizes them
• A PipelineTool wrapping OSMFetcher + ChatPromptBuilder to reduce token usage
• An Agent that uses this tool to plan walking itineraries based on user prompts
• Example use case: visiting a church → studying in a cafe → ending at a pub

The agent is guided via a system prompt and handles tool invocation autonomously.

This notebook was added following reviewer feedback on my OpenStreetMap integration PR, to illustrate how the component can be used in an Agent-based application.

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[kacperlukawski]

Thanks for contributing this example, @grexrr. Let me apologize it took so long, but we're catching up with the community contributions. I really liked the idea, but left some minor comments!