feat: add llm providers example notebook (#263)

* Created example notebook for llm providers

* Added tc.query() call and moved model compatibility note in llm-providers example notebook

* Add llm-providers notebook to examples in mkdocs.yml

* Additional explanation on LLM providers and a formatting change

* add pydantic_ai.models.Model to TimeCopilot init llm type hint

* Fix .head() method call in llm-providers example notebook

* Swap model for explicit ollama llm provider example

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Co-authored-by: spolisar <[email protected]>

Author: spolisar