[orx-palette] Add ColorBrewer2, demos, update README (#363)

orx-palette/src/jvmDemo/kotlin/DemoPaletteStudio02.kt

@@ -0,0 +1,68 @@
+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.extra.palette.PaletteStudio
+
+/**
+ * Demonstrates how to create a design using PaletteStudio.
+ * Press the `c` key to load a random palette.
+ *
+ */
+fun main() = application {
+    configure {
+        title = "Palette"
+        width = 720
+        height = 720
+    }
+    program {
+        val paletteStudio = PaletteStudio()
+
+        val colors = mutableListOf<ColorRGBa>()
+
+        fun fillColors() {
+            for (n in 0..36) {
+                when (n) {
+                    12 -> paletteStudio.loadCollection(PaletteStudio.Collections.TWO)
+                    24 -> paletteStudio.loadCollection(PaletteStudio.Collections.THREE)
+                }
+
+                val color = paletteStudio.colors.random()
+
+                colors.add(color)
+            }
+        }
+
+        keyboard.keyDown.listen {
+            if (it.name == "c") {
+                colors.clear()
+                fillColors()
+            }
+        }
+
+        fillColors()
+
+        extend {
+            drawer.clear(paletteStudio.background)
+
+            val size = 120.0
+            val radius = size / 2.0
+
+            for (x in 0 until 6) {
+                for (y in 0 until 6) {
+                    val index = x + y * 6
+                    val color = colors[index]
+                    val x = size * x
+                    val y = size * y
+
+                    drawer.fill = color
+                    drawer.stroke = color
+
+                    if (index <= 11 || index > 23) {
+                        drawer.circle(x + radius, y + radius, radius)
+                    } else {
+                        drawer.rectangle(x, y, size, size)
+                    }
+                }
+            }
+        }
+    }
+}