README.md: update leaderboard

commit generated automatically from
https://github.com/fxnn/adventofcode2024/actions/runs/12397865770

Author: fxnn

README.md

@@ -5,7 +5,7 @@ See https://adventofcode.com/2024
 
 [//]: # (LEADERBOARD_BEGIN)
 
-> user **fxnn** (16 stars, last one at 2024-12-18T16:54:12Z)
+> ![16 stars](https://img.shields.io/badge/16-%E2%AD%90_stars-gold) user **fxnn** (last one at 2024-12-18T16:54:12Z)
 
 [//]: # (LEADERBOARD_END)