add example config

config/config-example.yml

+# rename this file to config.yml and insert correct values
+
+credentials:
+  token: invenio-token
+
+dbrepo:
+  host: https://dbrepo1.ec.tuwien.ac.at/
+  credentials:
+    username: username
+    password: password
+  container-id: 15
+  database-id: 15
\ No newline at end of file