Fixes and move to jvmDemo (#286)

orx-fx/src/jvmDemo/kotlin/DemoPost01.kt

@@ -0,0 +1,29 @@
+import org.openrndr.WindowMultisample
+import org.openrndr.application
+import org.openrndr.extra.fx.Post
+import org.openrndr.extra.fx.blend.Add
+import org.openrndr.extra.fx.blur.ApproximateGaussianBlur
+import org.openrndr.shape.Circle
+import kotlin.math.cos
+
+fun main() = application {
+    configure {
+        windowResizable = true
+    }
+    program {
+        extend(Post()) {
+            val blur = ApproximateGaussianBlur()
+            val add = Add()
+            post { input, output ->
+                blur.window = 50
+                blur.sigma = 50.0 * (cos(seconds) * 0.5 + 0.5)
+                blur.apply(input, intermediate[0])
+                add.apply(arrayOf(input, intermediate[0]), output)
+            }
+        }
+        extend {
+            drawer.circle(width / 2.0, height / 2.0, 100.0)
+        }
+    }
+}
+