Add missing Palettes headline to Readme.md

Change-Id: I03f232ac692a66c5921614839578f9fd818efe1d
diff --git a/Readme.md b/Readme.md
index fa787cc..fd146e6 100644
--- a/Readme.md
+++ b/Readme.md
@@ -80,6 +80,7 @@
 ```
 ![](./man/figures/Readme-Example-3.png)<!-- -->
 
+## Palettes
 ### Default: Adapted D3 based Palette
 ```R
 library(scales)