The ports are rather straight forward and I have purposefully written
the documentation to be beginner friendly.
Note, I have diverged from Idris1 over the naming of the projection
functions to make them consistent with `Pair` and `DPair`.
Backed by Data.IOArray. Also moved the array external primitives to a
separate module Data.IOArray.Prims, since the next step is to add a
linear bounded array type where the bounds checks are done at compile
time, so we'll want to read and write without bounds likes.
