mfrw and kevinburke fmt: add example for Fscanln
Updates golang/go#27376.

Change-Id: I9f33233f1aafa10941a63fcb4e49d351ea7ee246
Reviewed-on: https://go-review.googlesource.com/132675
Reviewed-by: Kevin Burke <kev@inburke.com>
Run-TryBot: Kevin Burke <kev@inburke.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Latest commit 579768e Aug 31, 2018