Update README.md

Author: wakened2024

Diff for: README.md

@@ -2,6 +2,7 @@
 [![PyPI](https://badge.fury.io/py/gymnasium.svg)](https://badge.fury.io/py/gymnasium)
 [![arXiv](https://img.shields.io/badge/arXiv-2407.17032-b31b1b.svg)](https://arxiv.org/abs/2407.17032)
 [![pre-commit](https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit&logoColor=white)](https://pre-commit.com/)
+[![License](https://img.shields.io/github/license/Farama-Foundation/Gymnasium)](https://github.com/Farama-Foundation/Gymnasium/blob/main/LICENSE)
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 
 <p align="center">