Make the function signature less prominent, add an early example to docs

Signed-off-by: Nick Cameron <nrc@ncameron.org>

docs/kcl-std/functions/std-sketch-polygon.md

@@ -8,17 +8,19 @@ layout: manual
 Create a regular polygon with the specified number of sides that is either inscribed or circumscribed around a circle of the specified radius.
 
 ```kcl
-polygon(
-  @sketchOrSurface: Sketch | Plane | Face,
-  radius: number(Length),
-  numSides: number(_),
-  center: Point2d,
-  inscribed?: bool,
-): Sketch
+// Create a regular hexagon inscribed in a circle of radius 10
+hex = startSketchOn(XY)
+  |> polygon(
+       radius = 10,
+       numSides = 6,
+       center = [0, 0],
+       inscribed = true,
+     )
+
+example = extrude(hex, length = 5)
+
 ```
 
-
-
 ### Arguments
 
 | Name | Type | Description | Required |
@@ -34,6 +36,18 @@ polygon(
 [`Sketch`](/docs/kcl-std/types/std-types-Sketch) - A sketch is a collection of paths.
 
 
+### Function signature
+
+```kcl
+polygon(
+  @sketchOrSurface: Sketch | Plane | Face,
+  radius: number(Length),
+  numSides: number(_),
+  center: Point2d,
+  inscribed?: bool,
+): Sketch
+```
+
 ### Examples
 
 ```kcl