Add missing rlang dependency in DESCRIPTION

Change-Id: I50749277dc1f3fb91d5ec944fa4cb8b173037f32
diff --git a/DESCRIPTION b/DESCRIPTION
index b0d7359..669bd69 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -42,6 +42,7 @@
     methods,
     PTXQC,
     purrr,
+    rlang,
     stringr,
     urltools,
     xml2