docs: add more badges and style them as flat boxes

Author: 56kyle

README.md

@@ -6,11 +6,16 @@
   </a>
 </h1>
 
-[![uv](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/uv/main/assets/badge/v0.json)](https://github.com/astral-sh/uv)
+<!-- badges-begin -->
 
-[![Python demo status](https://github.com/robust-python/cookiecutter-robust-python/actions/workflows/python-demo.yml/badge.svg)](https://github.com/robust-python/robust-python-demo/actions)
+[![Maturin User Guide](https://img.shields.io/badge/user-guide-brightgreen?logo=readthedocs&style=flat-square)](https://robust-python.dev/cookiecutter)
+[![uv](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/uv/main/assets/badge/v0.json&style=flat-square)](https://github.com/astral-sh/uv)
+[![Python Versions](https://img.shields.io/pypi/pyversions/robust-python-demo?style=flat-square)](https://github.com/robust-python/cookiecutter-robust-python)
+[![Python demo status](https://github.com/robust-python/cookiecutter-robust-python/actions/workflows/python-demo.yml/badge.svg?style=flat-square)](https://github.com/robust-python/robust-python-demo/actions)
 [![Maturin demo status](https://github.com/robust-python/cookiecutter-robust-python/actions/workflows/maturin-demo.yml/badge.svg)](https://github.com/robust-python/robust-maturin-demo/actions)
-[![Discord](https://img.shields.io/badge/Discord-%235865F2.svg?logo=discord&logoColor=white)](https://discord.gg/robust-python)
+[![Discord](https://img.shields.io/badge/Discord-%235865F2.svg?logo=discord&logoColor=white&style=flat-square)](https://discord.gg/robust-python)
+
+<!-- badges-end -->
 
 # cookiecutter-robust-python