Add runtime OAuth2 browser flow demos with httr and httr2

Change-Id: If244a6c6c68115f52125189445c30c167c61b13b
diff --git a/demo/OAuthBrowserflowHttr2.R b/demo/OAuthBrowserflowHttr2.R
new file mode 100644
index 0000000..b67564e
--- /dev/null
+++ b/demo/OAuthBrowserflowHttr2.R
@@ -0,0 +1,14 @@
+library(RKorAPClient)
+library(httr2)
+library(kableExtra)
+
+token <- oauth_client( id = "773NHGM76N7P9b6rLfmpM4",
+    token_url = "https://korap.ids-mannheim.de/api/v1.0/oauth2/token") %>%
+  oauth_flow_auth_code( scope = "search match_info",
+    auth_url = "https://korap.ids-mannheim.de/settings/oauth/authorize")
+
+new("KorAPConnection", verbose = TRUE, accessToken = token$access_token) %>%
+  collocationAnalysis("focus([marmot/p=ADJA] {Gendern})", leftContextSize=1, rightContextSize=0) %>%
+  mutate(collocate = paste0('<a href="', webUIRequestUrl, '">', collocate, '</a>')) %>%
+  select(collocate, O, pmi, mi2, mi3, logDice, ll) %>%
+  kable(escape = FALSE, caption = "Adjective collocates of 'Gendern'") %>% kable_styling()