SLING-7167 Adjust READMEs

add uniform header linking to Sling project

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1810885 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/README.md b/README.md
index 10d25e3..28aefdf 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
-Apache Sling Authentication XING Login
-======================================
+# Apache Sling Authentication XING Login
+
+This module is part of the [Apache Sling](https://sling.apache.org) project.
 
 * uses the cookie-based “[Login with XING](https://dev.xing.com/plugins/login_with)” for authentication
 * allows creating and updating JCR users based on supplied user data from XING