Add orx-shapes demos

orx-shapes/src/demo/kotlin/DemoRoundedRectangle.kt

@@ -0,0 +1,23 @@
+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.extensions.SingleScreenshot
+import org.openrndr.extra.shapes.RoundedRectangle
+import kotlin.math.cos
+
+fun main() = application {
+    program {
+        // -- this block is for automation purposes only
+        if (System.getProperty("takeScreenshot") == "true") {
+            extend(SingleScreenshot()) {
+                this.outputFile = System.getProperty("screenshotPath")
+            }
+        }
+        extend {
+            drawer.fill = ColorRGBa.WHITE
+            drawer.stroke = ColorRGBa.PINK
+            val radius = cos(seconds) * 20.0 + 20.0
+            val rectangle = RoundedRectangle(50.0, 50.0, width - 100.0, height - 100.0, radius)
+            drawer.contour(rectangle.contour)
+        }
+    }
+}