Update conf.py - added sphinx-minipres extension

With this extension the page can be transformed into something which is more convenient for presentation:

https://coderefinery.github.io/sphinx-lesson/presentation-mode/

by simply adding ?pres or ?minipres to the url.

We can then work on each section to try to fit it into a reasonable size - what would typically go into one slide. And maybe highlight words in bold face to make it easier for presenter and students to follow along.

Added also to the unix-intro conf.py