Add format check badge to README

This commit updates the README to include a badge for the format check GitHub Action workflow. It improves visibility of the project's code formatting status directly in the documentation.

Author: nicholasadamou

README.md

@@ -1,4 +1,4 @@
-# NeetCode 150 Solutions [![Python Unit Tests](https://github.com/daily-coding-problem/neetcode-150/actions/workflows/python-unittests.yml/badge.svg)](https://github.com/daily-coding-problem/neetcode-150/actions/workflows/python-unittests.yml)
+# NeetCode 150 Solutions [![Python Unit Tests](https://github.com/daily-coding-problem/neetcode-150/actions/workflows/python-unittests.yml/badge.svg)](https://github.com/daily-coding-problem/neetcode-150/actions/workflows/python-unittests.yml) [![Format Check](https://github.com/daily-coding-problem/neetcode-150/actions/workflows/format-check.yml/badge.svg)](https://github.com/daily-coding-problem/neetcode-150/actions/workflows/format-check.yml)
 
 ![Python](https://img.shields.io/badge/-Python-3776AB?style=flat-square&logo=python&logoColor=white)
 ![Pytest](https://img.shields.io/badge/-Pytest-0A9EDC?style=flat-square&logo=pytest&logoColor=white)