The 12-factor principles link is broken

The link in the README for the 12-factor principles is broken, I'm getting a 403 response. Maybe you could link to an alternative resource that also explains these principles?

**Link**: http://12factor.net

**Screenshot**:

<img width="1436" alt="Screen Shot 2023-07-07 at 8 14 11 PM" src="https://github.com/theskumar/python-dotenv/assets/4128208/97faa90e-6cfb-422d-91cf-0dc915b495bc">