Add demo for comparing written vs. spoken frequencies

Change-Id: I9416c8b199c64e55e10d40db0e475cf6de488b40
diff --git a/demo/00Index b/demo/00Index
index 117e857..f2e526a 100644
--- a/demo/00Index
+++ b/demo/00Index
@@ -5,3 +5,4 @@
 regional                  Map plot regional frequencies of query expression
 mosaicplot                Visualize frequencies of alternative query terms in relation to other variables
 highcharter-example       Visualize frqequencies of optionally alternative terms over time with interactive HTML and JavaScript elements using the package highcharter as wrapper for Highcharts
+writtenVsSpoken           Compare frequencies in written vs. spoken corpora