How to self-host a website like croxyproxy.com?

I’m looking to self-host a web-based proxy similar to CroxyProxy. The idea is to have a simple web interface where users can enter a URL and browse through my server, kind of like a mix between a traditional proxy and a lightweight VPN alternative.

I know regular HTTP/HTTPS proxies exist, but CroxyProxy works with absolutely no setup, which is a requirement since I want to use it on very restricted computers. How would I go about setting up something like this? Are there any open-source projects or frameworks that could help?