README.md: update

Fix the broken formatting (wrong headlines, missing line breaks in
blocks of commands) and move the configuration and escript sections
below the running section.

Add the command that fixeria suggested for running it with one shell
command.

Old: https://gitea.osmocom.org/erlang/osmo_dia2gsup/src/branch/master/README.md
New: https://gitea.osmocom.org/osmith/osmo_dia2gsup/src/branch/master/README.md

Change-Id: Ib96f42ca0066ba2f6d0d783f6bf1764cbfee544f

README.md

@@ -1,42 +1,51 @@
-= Osmocom DIAMETER -> GSUP translator =
+# Osmocom DIAMETER -> GSUP translator
 
 This project implements a proxy translating Diameter into GSUP, hence allowing
 Diameter clients connecting to GSUP server. This allows, for instance, using
 OsmoHLR as an HSS used by 4G/5G nodes.
 
-== Building ==
+## Building
 
 Install erlang and rebar3 packages (not "rebar", that's version 2! You may need
 to compile it from source in some distros).
 
+```
 $ rebar3 compile
 $ rebar3 escriptize
+```
 
-== Testing ==
+## Testing
 
 Unit tests can be run this way:
+```
 $ rebar3 eunit
+```
 
-== Running ==
+## Running
 
 Once osmo\_dia2gsup is built, you can start it this way:
 
+```
 $ rebar3 shell
-
-In the erlang shell:
-```
 1> osmo_dia2gsup:start().
 ```
 
-== Configuration ==
+Passing a config file:
 
+```
 $ rebar3 shell --config ./examples/sys.config
-```
 1> osmo_dia2gsup:start().
 ```
 
-== Run as an escript ==
+Running it with one shell command:
 
+```
+$ rebar3 shell --config ./examples/sys.config --eval "osmo_dia2gsup:start()."
+```
+
+Running it as an escript:
+
+```
 $ rebar3 escriptize
 $ ERL_FLAGS='-config ./examples/sys.config' _build/default/bin/osmo-dia2gsup
-
+```