Add runtime OAuth2 browser flow demos with httr and httr2

Change-Id: If244a6c6c68115f52125189445c30c167c61b13b
diff --git a/demo/00Index b/demo/00Index
index 6000d36..2b86b41 100644
--- a/demo/00Index
+++ b/demo/00Index
@@ -14,3 +14,5 @@
 frequency_by_country_highcharts Plot frequencies depending on country of publication using highcharter.
 collocation_score_by_country    Plot collocation scores depending on country of publication using ggplot2.
 pluralGenderVariants            Plot frequencies of the plular gender variants of a word over time.
+OAuthBrowserflowHttr2           Runtime OAuth2 browser flow demonstration using the httr2 package (adjective collocates of »Gendern«)
+OAuthBrowserflowHttr            Runtime OAuth2 browser flow demonstration using the httr package (query results for »Vöner« including KWICs)