Add bearing conversion docs example (#312)

Author: sargunv

docs/units/index.md

@@ -63,7 +63,9 @@ converting between scalars, lengths, and areas as needed.
 
 `Bearing` represents an absolute geographic heading (e.g., North, East), while `Rotation` represents
 a relative angular displacement. In Kotlin, bearings can be rotated using operators, and the
-difference between two bearings is a rotation.
+difference between two bearings is a rotation. To convert a `Bearing` to a numeric angle, first
+choose a reference direction and range, such as `0..360` degrees clockwise from north or `-180..180`
+degrees relative to north.
 
 === "Kotlin"
 

units/src/commonTest/kotlin/org/maplibre/spatialk/units/KotlinDocsTest.kt

@@ -37,6 +37,10 @@ class KotlinDocsTest {
         val turnedRight: Bearing = heading + 90.degrees
         val turnedLeft: Bearing = heading - 45.degrees
         val diff: Rotation = turnedRight - turnedLeft
+
+        val bearing: Bearing = Bearing.Northwest
+        val clockwiseFromNorth: Double = (bearing - Bearing.North).inDegrees
+        val signedFromNorth: Double = Bearing.North.smallestRotationTo(bearing).inDegrees
         // --8<-- [end:bearings]
     }