Tutorial on conformal time series regression with puncc

[M-Mouhcine]

This PR adds a tutorial on conformal time series regression using puncc. It walks through how to apply different conformal prediction methods (OSSCP, WSCP, EnbPI) to time series data, with explanations, code examples, and visualizations. The goal is to provide a hands-on, beginner-friendly guide that highlights the use cases, strengths, and limitations of each method in a time-dependent setting.