Add screenshot generation

orx-noise/src/demo/kotlin/DemoGradientPerturb2D.kt

@@ -1,10 +1,10 @@
 import org.openrndr.application
 import org.openrndr.color.ColorRGBa
 import org.openrndr.draw.colorBuffer
+import org.openrndr.extensions.SingleScreenshot
 import org.openrndr.extra.noise.gradientPerturbFractal
 import org.openrndr.extra.noise.simplex
 import org.openrndr.math.Vector2
-import org.openrndr.math.Vector3
 import kotlin.math.absoluteValue
 
 fun main() {
@@ -12,6 +12,11 @@ fun main() {
         program {
             val cb = colorBuffer(width, height)
             val shad = cb.shadow
+            if (System.getProperty("takeScreenshot") == "true") {
+                extend(SingleScreenshot()) {
+                    this.outputFile = System.getProperty("screenshotPath")
+                }
+            }
             extend {
                 for (y in 0 until height) {
                     for (x in 0 until width) {