Readme: add video on getting and persisting an access token

Change-Id: I4935bf62d4abbef4e443b9af9bb2cfdf3e8e187a
diff --git a/Readme.md b/Readme.md
index 4f0dbe9..f7b0832 100644
--- a/Readme.md
+++ b/Readme.md
@@ -102,6 +102,10 @@
 persistAccessToken(kco)
 ```
 
+The whole process is shown in this video:
+
+https://korap.github.io/RKorAPClient/man/figures/RKorAPClient-get-and-persists-accessToken.mp4
+
 
 ## Demos