Add linked qrcode: qrlink

Change-Id: I344ae90b5cc6aad9f61ff5ac9e42fe8680af7164
diff --git a/DESCRIPTION b/DESCRIPTION
index 6aec2a2..497fc0d 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -23,6 +23,7 @@
 BugReports: https://github.com/brentthorne/posterdown/issues
 Imports: 
     pagedown,
+    qrcode,
     rmarkdown,
     yaml
 Suggests: knitr