Add guidance for training courses that run on multiple operating systems

[julian-cable]

To accommodate the needs of cloud services training courses that run on multiple operating systems, review and consider adding relevant pieces of guidance from the CS220 Consistency Guide to the style guide:

https://docs.google.com/document/d/1ksbQvQ8SqQM7vAgulDJodt3xTW4KE6bg8Lo0-Iv4JIw/edit#heading=h.i832mlfrmg60