Make it easy to install ly on runit systems e.g. void (#431)

* Make it easy to install ly on runit systems e.g. void

* Tidy up runit section in readme

Co-authored-by: Daniel Haarhoff <daniel@rknt.de>

res/ly-runit-service/run

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+tty=${PWD##*-}
+
+[ -r conf ] && . ./conf
+
+if [ -x /sbin/getty -o -x /bin/getty ]; then
+	# busybox
+	GETTY=getty
+elif [ -x /sbin/agetty -o -x /bin/agetty ]; then
+	# util-linux
+	GETTY=agetty
+fi
+
+exec setsid ${GETTY} ${GETTY_ARGS} -nl /usr/bin/ly tty2 "${BAUD_RATE}" "${TERM_NAME}"