Update README stars

Author: colematt

README.md

@@ -2,7 +2,7 @@
 
 [![Update README ⭐](https://github.com/colematt/advent-code/actions/workflows/update-readme.yml/badge.svg?branch=main)](https://github.com/colematt/advent-code/actions/workflows/update-readme.yml)
 ![Current year](https://img.shields.io/badge/year%20🎄-2025-blue)
-![Current day](https://img.shields.io/badge/day%20📅-15-blue)
+![Current day](https://img.shields.io/badge/day%20📅-16-blue)
 ![This year's stars](https://img.shields.io/badge/stars%20⭐-15-yellow)
 ![This year's completed days](https://img.shields.io/badge/days%20completed-7-red)