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

orx-palette/src/jvmDemo/kotlin/DemoPaletteStudio01.kt

@@ -0,0 +1,31 @@
+import org.openrndr.application
+import org.openrndr.extra.palette.PaletteStudio
+
+/**
+ * Demonstrates how to access palette colors using PaletteStudio.
+ * A new random palette is loaded every 60 animation frames.
+ */
+fun main() = application {
+    configure {
+        width = 720
+        height = 720
+    }
+    program {
+        val paletteStudio = PaletteStudio()
+
+        // Choose a specific initial palette
+        paletteStudio.select(11)
+
+        extend {
+            if(frameCount % 60 == 50) {
+                paletteStudio.randomPalette()
+            }
+            drawer.clear(paletteStudio.background)
+
+            paletteStudio.colors2.forEachIndexed { i, color ->
+                drawer.fill = color
+                drawer.circle(drawer.bounds.center, 300.0 - i * 40.0)
+            }
+        }
+    }
+}