Update README badges (#145)

The automated badge retrieval from PyPI did not work properly so I tuned the colors and badges myself using lightcone colour scheme

Author: aboucaud

README.md

@@ -1,9 +1,9 @@
 # lightcone-cli
 
-[![License](https://img.shields.io/badge/License-BSD_3--Clause-blue.svg)](https://opensource.org/licenses/BSD-3-Clause)
-[![Python](https://img.shields.io/pypi/pyversions/lightcone-cli)](https://pypi.org/project/lightcone-cli/)
-[![Tests](https://github.com/LightconeResearch/lightcone-cli/actions/workflows/tests.yml/badge.svg)](https://github.com/LightconeResearch/lightcone-cli/actions/workflows/tests.yml)
-[![PyPI](https://img.shields.io/pypi/v/lightcone-cli)](https://pypi.org/project/lightcone-cli/)
+[![License](https://img.shields.io/badge/License-BSD_3--Clause-426b78.svg?style=flat)](https://opensource.org/licenses/BSD-3-Clause)
+[![Python](https://img.shields.io/badge/python-3.11%20%7C%203.12%20%7C%203.13-4e5a70?style=flat)](https://pypi.org/project/lightcone-cli/)
+[![PyPI](https://img.shields.io/pypi/v/lightcone-cli?style=flat&color=f8f7f3)](https://pypi.org/project/lightcone-cli/)
+[![Tests](https://img.shields.io/github/actions/workflow/status/LightconeResearch/lightcone-cli/tests.yml?style=flat&color=darkgreen)](https://github.com/LightconeResearch/lightcone-cli/actions/workflows/tests.yml)
 
 <!-- [![Ruff](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json)](https://github.com/astral-sh/ruff) -->