docs: add a simple example to use configuration file

Change-Id: I013f03779508bc3ee5bb378c357a5c94b40b74a0
---
M README.md
A examples/sys.config
2 files changed, 23 insertions(+), 1 deletion(-)


git pull ssh://gerrit.osmocom.org:29418/erlang/osmo_dia2gsup refs/changes/47/27647/1

diff --git a/README.md b/README.md
index 52c076a..4b52070 100644
--- a/README.md
+++ b/README.md
@@ -19,9 +19,19 @@
 
 == Running ==
 
-Once osmo_dia2gsup is built, you can start it this way:
+Once osmo\_dia2gsup is built, you can start it this way:
 
 $ rebar3 shell
 
 In the erlang shell:
+```
 1> osmo_dia2gsup:start().
+```
+
+== Configuration ==
+
+$ rebar3 shell --config ./examples/sys.config
+```
+1> osmo_dia2gsup:start().
+```
+
diff --git a/examples/sys.config b/examples/sys.config
new file mode 100644
index 0000000..8814893
--- /dev/null
+++ b/examples/sys.config
@@ -0,0 +1,12 @@
+[{osmo_dia2gsup, [
+        {hlr_ip, "127.0.0.1"},
+        {hlr_port, 4222},
+
+        {diameter_ip, "127.0.0.4"},
+        {diameter_port, 3868},
+        {diameter_proto, sctp},
+
+        {origin_host, "hss.localdomain"},
+        {origin_realm, "localdomain"},
+        {vendor_id, 0}
+]}].

