add numbers and letters to on-screen keyboard for when a teacher is presenting using free math, with a smart board

[jaltekruse]

users will not always have a keyboard in in front of them, a major use case is presenting with a smartboard or similar device using a projector or sceen.

It would also be nice to improve the experience on mobile, currently users will have both the math keyboard and their default mobile keyboard showing on the screen at once when a math mathquill box is selected.

One good thing about showing the default mobile keyboard is that other languages are supported. Might need to be a follow up but also consider localizing the on-screen keyboard for different languages and regions.