Appending static arrays

[Nordlöw via Digitalmars-d-learn]

I'm want to define a specialization of `append()` that takes only 
static arrays as inputs and returns a static array being the sum 
of the lengths of the inputs.

Have anybody already implemented this?
If not, I'm specifically interested in how to most conveniently 
infer the length (as an enum) of the returned static array from 
the `.length`s of inputs (which of course must be enum-values 
too).