Added builtin function min() and max()#1721

Hello,

I have added functionality for the min() and max() operations.
I am unsure if this project is still actively maintained, but I would like to contribute and help keep it alive.

As a Go developer, I have found the REPL to be a convenient and efficient tool for quickly testing concepts, and I rely heavily on yaegi in my workflow. I am enthusiastic about contributing to the project.

I have opened a pull request with these changes. If anyone has time to review it, I would greatly appreciate your feedback.

Thank you!

I think the project is used by Traefik for running plugins, it's maintained, but not a lot is happening. The forum here is slow, too, usually no devs here. Just give it some time.