Add if serial-port is in use

src/hooks/connect-plug-zui-store

@@ -1,6 +1,5 @@
 #!/usr/bin/env bash
 
-snapctl get --slot :zui-store serial > "${SNAP_DATA}.zui-serial"
 $SNAP/bin/cpy-2-zui
 
 logger "Connected ZUI (from: z2m)"

src/hooks/prepare-plug-zui-store

@@ -1,3 +1,4 @@
 #!/usr/bin/env bash
 
-snapctl set :zui-store plugattribute="$(snapctl get -d server mqtt session)"
+snapctl set :zui-store z2mconfig="$(snapctl get -d server mqtt session)"
+snapctl set :zui-store z2mserial="$(snapctl is-connected serial-port && echo 1 || echo 0)"