voro_margin: fix and add wikipedia

content/en/docs/attrs/voro_margin.md

@@ -13,6 +13,9 @@ title: voro_margin
 types:
 - double
 used_by: G
-description: Factor to scale up drawing to allow margin for expansion i
+description: Tuning margin of Voronoi technique
 ---
-Voronoi technique. `dim' = (1+2*margin)*dim`.
+
+Factor to scale up drawing to allow margin for expansion in
+[Voronoi technique](https://en.wikipedia.org/wiki/Voronoi_diagram).
+`dim' = (1+2*margin)*dim`.