Add getting started tutorials

[mrmer1]

This pull request adds a new tutorial notebook for getting started with the Cohere platform. The tutorial is split into seven parts, each focusing on a specific use case:

• Part1: Installation and Setup
• Part 2: Text Generation
• Part 3: Chatbots
• Part 4: Semantic Search
• Part 5: Reranking
• Part 6: Retrieval-Augmented Generation (RAG)
• Part 7: Agents with Tool Use

The tutorial uses a hands-on approach, where users build an onboarding assistant for new hires at a fictitious company called Co1t. Each part works as a standalone tutorial, but it is recommended to follow them sequentially.

Changes

• Add a new tutorial notebook `tutorial_pt1.ipynb covering installation and setup.
• Add a new tutorial notebook `tutorial_pt2.ipynb covering text generation.
• Add a new tutorial notebook `tutorial_pt3.ipynb covering chatbots.
• Add a new tutorial notebook `tutorial_pt4.ipynb covering semantic search.
• Add a new tutorial notebook `tutorial_pt5.ipynb covering reranking.
• Add a new tutorial notebook `tutorial_pt6.ipynb covering retrieval-augmented generation (RAG).
• Add a new tutorial notebook `tutorial_pt7.ipynb covering agents with tool use.