Introduce OsmoTRX manual

Change-Id: I19ee9d6cda02fb7200c96c0ac129e69825b096cd
diff --git a/doc/manuals/vty/trx_vty_additions.xml b/doc/manuals/vty/trx_vty_additions.xml
new file mode 100644
index 0000000..a4c675e
--- /dev/null
+++ b/doc/manuals/vty/trx_vty_additions.xml
@@ -0,0 +1,2 @@
+<vtydoc xmlns='urn:osmocom:xml:libosmocore:vty:doc:1.0'>
+</vtydoc>