making-the-grades: explain static_cast

[ErikSchierboom]

I don't see any mention in the instructions on how to actually use static_cast. We don't necessarily need an example, but maybe mention that static_cast is a function (or at least can be called as a function)?

[vaeng]

static_cast can be found earlier in the tree under the numbers concept. Maybe a short refresher is better?

[ErikSchierboom]

Ah, I missed that. My solution there doesn't use static_cast, which might be why it didn't stick.