Create auth.json.sample

Sample auth file like repository Magento Enterprise Cloud Edition

Author: rafaelstz

auth.json.sample

@@ -0,0 +1,8 @@
+{
+   "http-basic": {
+      "repo.magento.com": {
+         "username": "<public-key>",
+         "password": "<private-key>"
+      }
+   }
+}