document const items

[jesse99]

Not sure these are documented at all, but it would be nice to list which types can be used with const items. In particular I think vectors and strings (yay!) can now be const items.

[kud1ing]

I'd be happy if you could explain the need for the extra "const" keyword.
I was surprised when i found

const REPEAT: int = 5;

in the tutorial. Wouldn't it be possible to do

let REPEAT: int = 5;

also for global constants? Since REPEAT is not mutable it is constant?
Could you also have

const REPEAT: mut int = 5;

?

[brson]

I added a section to the tutorial on constants, but haven't addressed @Lenny222's concerns.