Add `diamond` exercise

[ErikSchierboom]

During this exercise, I found that having a constant defined would cause the stack space check to fail.

[glennj]

During this exercise, I found that having a constant defined would cause the stack space check to fail.

Were you expecting the constant to exist on the stack?

[ErikSchierboom]

I did not expect that, but maybe that's just how it works

[glennj]

According to the words list:

This is essentially syntactic sugar for the prior method of creating a new word containing the value x.

So I assume 42 constant answer is the same as : answer 42 ;