msmtp: add test.sh

This file ensures that msmtp is run tested inside GitHub Actions
to help to ensure that this application is compiled and run
tested for OpenWrt master.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

mail/msmtp/test.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+case "$1" in
+        msmtp)
+                msmtp --version | grep "$2"
+                ;;
+esac