The map doesn't appear

Hello everyone,

I am following his tutorial https://codepen.io/yuyazz/pen/MWaoeOP.

Here is my code: https://github.com/lea131211/interactivemapdoesntwork.git

Do you see, what’s wrong? I am completely new to coding.

Thank you!

Some explanation of the tutorial I followed: (Créer une carte personnalisée avec Leaflet et markerCluster js - Copier coller