Add hint to run Wireproxy as system daemon in rc.d-based system (#164)

* Add hint for rc.d service

* Update README.md

---------

Co-authored-by: root <root@prox1.example.com>

rc.d/README.md

@@ -0,0 +1,21 @@
+# Running wireproxy with rc.d
+
+If you're on a rc.d-based distro, you'll most likely want to run Wireproxy as a systemd unit.
+
+The provided systemd unit assumes you have the wireproxy executable installed on `/bin/wireproxy` and a configuration file stored at `/etc/wireproxy.conf`. These paths can be customized by editing the unit file.
+
+# Setting up the unit
+
+1. Copy the `wireproxy` file from this directory to `/usr/local/etc/rc.d`.
+
+2. If necessary, customize the unit.
+   Edit the parts with `procname`, `command`, `wireproxy_conf`  to point to the executable and the configuration file.
+
+4. Add the following lines to `/etc/rc.conf` to enable wireproxy
+   `wireproxy_enable="YES"`
+
+5. Start wireproxy service and check status
+   ```
+   sudo service wireproxy start
+   sudo service wireproxy status
+   ```

rc.d/wireproxy

@@ -0,0 +1,30 @@
+#!/bin/sh
+#
+# PROVIDE: wireproxy
+# REQUIRE: DAEMON
+# KEYWORD: nojail
+#
+
+#
+# Add the following lines to /etc/rc.conf to enable wireproxy:
+#
+#wireproxy_enable="YES"
+#
+
+. /etc/rc.subr
+
+name=wireproxy
+rcvar=wireproxy_enable
+
+load_rc_config $name
+procname="/bin/wireproxy"
+
+wireproxy_enable=${wireproxy_enable:-"NO"}
+
+wireproxy_bin=/bin/wireproxy
+wireproxy_conf=/etc/wireproxy.conf
+
+command=${wireproxy_bin}
+command_args="-s -d -c ${wireproxy_conf}"
+
+run_rc_command "$1"