Add lens-person Haskell-specific exercise

lens-person.md

@@ -0,0 +1,5 @@
+Updating fields of nested records is kind of annoying in Haskell. One solution
+is to use [lenses](https://wiki.haskell.org/Lens).  Implement several record
+accessing functions using lenses, you may use any library you want. The test
+suite also allows you to avoid lenses alltogether so you can experiment with
+different approaches.

lens-person.yml

@@ -0,0 +1,5 @@
+---
+blurb: "(Haskell specific) use lenses to update nested records."
+common:
+    type: focus
+    focus: lenses