[orx-fft] Add orx-fft for a simple fast fourier transform routine

orx-fft/src/commonMain/kotlin/HannWindow.kt

@@ -0,0 +1,9 @@
+package org.openrndr.extra.fft
+
+import kotlin.math.PI
+import kotlin.math.cos
+
+class HannWindow : WindowFunction() {
+    override fun value(length: Int, index: Int): Float = 0.5f * (1f - cos((PI * 2.0 * index / (length - 1f)))
+        .toFloat())
+}