added systemd service

I hope this helps for CUPS

PKGBUILD

@@ -25,6 +25,8 @@ package() {
     rm -rf "$pkgdir/usr/share/cat-printer/build-"*
     rm -rf "$pkgdir/usr/share/cat-printer/dev-diary.txt"
     rm -rf "$pkgdir/usr/share/cat-printer/TODO"
+    rm -rf "$pkgdir/usr/share/cat-printer/systemd"
+    install -m644 "$srcdir/cat-printer-git/systemd/cat-printer.service" "$pkgdir/usr/lib/systemd/system/"
     cat <<EOF > "$pkgdir/usr/bin/cat-printer"
 #!/bin/sh
 cd /usr/share/cat-printer

systemd/cat-printer.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=A project that provides support to some Bluetooth Cat Printer models
+After=bluetooth.target network.target
+Requires=bluetooth.target network.target
+StartLimitIntervalSec=5
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/cat-printer-server -s
+Restart=on-failure
+DynamicUser=true
+
+[Install]
+WantedBy=multi-user.target