Add Quick Start to Readme

[ai-yann]

This PR introduces a restructured README file for the Cohere Examples repository, enhancing its organisation and clarity. The changes include:

• Renaming Sections: The sections 'Getting Started', 'LLM University', 'Cookbook', 'RAG', 'Agents', 'Summarization', and 'Others' have been renamed to 'Quick Start', 'LLM University', 'Cookbook', 'RAG', 'Agents', 'Summarization', and 'Others', respectively.
• Adding Subsections: The 'Quick Start' section now includes 'Installation' and 'Authentication' subsections, providing detailed instructions for setting up the Cohere Python SDK and authenticating with the CohMre API.
• Prerequisites: A new 'Prerequisites' section has been added, listing the requirements for using the repository, including Python 3.7 or higher, a Cohere API key, and familiarity with Jupyter notebooks.
• Consistent Formatting: The formatting of the README has been standardised, ensuring a consistent look and feel throughout the document.

[mrmer1]

to add both options - v1 and v2, with v2 as the preferred one.