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-math-polar.md

@@ -8,14 +8,18 @@ layout: manual
 Convert polar/sphere (azimuth, elevation, distance) coordinates to cartesian (x/y/z grid) coordinates.
 
 ```kcl
-polar(
-  angle: number(rad),
-  length: number(Length),
-): Point2d
+exampleSketch = startSketchOn(XZ)
+  |> startProfile(at = [0, 0])
+  |> line(end = polar(angle = 30deg, length = 5), tag = $thing)
+  |> line(end = [0, 5])
+  |> line(end = [segEndX(thing), 0])
+  |> line(end = [-20, 10])
+  |> close()
+
+example = extrude(exampleSketch, length = 5)
+
 ```
 
-
-
 ### Arguments
 
 | Name | Type | Description | Required |
@@ -28,6 +32,15 @@ polar(
 [`Point2d`](/docs/kcl-std/types/std-types-Point2d) - A point in two dimensional space.
 
 
+### Function signature
+
+```kcl
+polar(
+  angle: number(rad),
+  length: number(Length),
+): Point2d
+```
+
 ### Examples
 
 ```kcl