docs: update readme with example link

Author: pdmnyberg

README.md

@@ -42,4 +42,8 @@ are defined, all questionSets will be returned.
 are 'pie' and 'bar'. Defaults to 'pie' if not defined.
 * colors: A list of hex colors to be used for plotting. Defaults to ELIXIR colors
 * endpoint: The API endpoint to get the data from. Defaults
-to "https://tmd.elixir-europe.org/metrics"
+to "https://tmd.elixir-europe.org/metrics"
+
+### Example usage
+
+A very simple example usage of the widget script can be seen in `example.html` and it can be previewed at https://elixir-europe-training.github.io/Training-Metrics-Database-widget/example.html