Improve tutorial experience on short screens.

[ssande-fwd]

Is your feature request related to a problem? Please describe.
Tutorial content gets cut off on short screens, both in the modal and in the upper portion of the editor. At Forward Education workshops it's a recurring issue that our customers can't find the next button. I recall personally experiencing this at first too.

Describe the solution you'd like
A prominent scroll bar would cue the user that there is more content that they can scroll to. Currently the scroll bar only shows on hover. Moving or reworking the navigation could avoid scenarios where all of the tutorial content is or seems to be present with the navigation being hidden. For example, just taking what is now at the bottom and moving it to the top could be an improvement. Or have it always present like it is for the modal.

Describe alternatives you've considered
A prominent scrollbar could be enough on it's own to prevent confusion .

Additional context
https://makecode.microbit.org/#tutorial:https://github.com/climate-action-kits/pxt-fwd-edu/ms-aquaticgarbage-use