Add information on secret file to readme

Change-Id: I22148257c9307cb5474d798d2f826f7f2752cc5a
diff --git a/package.json b/package.json
index dbe9e07..6e451ba 100755
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "Kalamar",
   "description": "Mojolicious-based Frontend for KorAP",
   "license": "BSD-2-Clause",
-  "version": "0.38.0",
+  "version": "0.39.0",
   "pluginVersion": "0.2",
   "engines": {
     "node": ">=6.0.0"