Mention requirement for compatible firmware

[okin]

While it is obvious to probably most veteran users Vial does require a board to have a Vial-compatible firmware installed.
I believe this should be mentioned in the docs in a prominent place.

Not sure where to put this is the best place. Front page or the First time use come to mind as this is probably where users start to look first.
I'd say front page is good because this is what most people see but since this is already mostly text it might be overlooked there. First time use might be a better candidate but then we probably should introduce a section like Preparing your keyboard or something along the lines.

For many probably the next questions are:

• is my board compatible?
• where do I find a firmware?
• how do I get it onto my board?

I think these should also be adressed in order to help new users understand the required steps. Maybe we could add another page specific to this questions.

What do you think?