Add sprint proposal for Feature-engine modernization

[solegalli]

This document outlines the proposal for a sprint focused on modernizing the Feature-engine API to improve flexibility and performance while maintaining backward compatibility.

🖼️ Preview available 🖼️ : https://ep-website--1731.org.readthedocs.build/

[egeakman]

Hi @solegalli, thanks so much for proposing your project for the sprints!

I noticed the build is currently failing with this message:

[ERROR] Error: No headlines allowed in description. [feature-engine-sprint-proposal]

To fix this, you can just swap out the Markdown headings (#, ##, etc.) for bold text (**) or numbered/bullet-point lists.

While you're making that tweak, could you also condense the description a bit? We encourage shorter descriptions so it's fair to all projects and easier for attendees to scan through their options. For a good sense of the target length, feel free to check out last year's sprint projects.

Thanks!