implement Dashboard-Version preview

maybe not an optimal solution, particularly because iframe is a bit awkward. Unfortunately I couldn't find any other tags that allowed to load static external text files, except for this. If you have a better version in mind, let's talk about that.

The iframe has a tiny bit of text-styling and allows for setting fixed version of the dashboard, so it is known to the user immediately.

The commit also involves syntax cleaning to make sure my changes do not break the syntax.