Distinctive Prerequisite section per OS

[markusjura]

This issue needs a change in conductr-doc and Typesafe.com

How to install docker and python3 is different on MacOS, Windows, Ubuntu, Debian, etc. Therefore, the prerequisite section should be separate for each OS. An example of what you might do is have separate sections for each, stacked vertically down the page, at the start you click to select which one you want and the page will scroll down to it (don't just use anchor links, use a smooth scroll so that the user can clearly see that they are being scrolled down), and then at the end of the OS specific instructions, have another link that scrolls you down to the rest of the instructions. The docker installation page has a good example of the scrolling I'm talking about: https://www.docker.com/products/docker