feat: Let it snow! Add a toggleable snow effect to the UI

Haha, love that idea! A snowy effect is a classic fun feature and a perfect "good first issue" because Streamlit makes it incredibly easy to do.

Here is a ready-to-post GitHub issue for it. This one is designed to be fun and very welcoming for a brand new contributor.

Title: feat: Let it snow! Add a toggleable snow effect to the UI

Description:

Let's add a bit of winter magic to the algorithm visualizer! This is a fun, purely cosmetic feature to make the app more delightful to use. Streamlit has a built-in command to create a beautiful falling snow effect.

The goal is to add this snow effect but also give the user control to turn it on and off.