Add comment about the demo page to root README

Author: grega

README.md

@@ -45,9 +45,10 @@ const result = explain({
 
 // result.html is a ready-made snippet
 // or use result.title, result.summary, result.steps, result.patch, result.trace
-
 ```
 
+See the [demo](demo/README.md) for a full set of examples.
+
 ## Development
 
 ### Prerequisites