[preflight] Add check for logger dependency

'logger' is required to facilitate logging to the journaling system.

cfddns.sh

@@ -373,6 +373,10 @@ fi
 if [ ! -f "$accountFile" ] || [ ! -s "$accountFile" ]; then
     badParam errMsg "Cannot find Cloudflare credentials file (${accountFile}). Exiting."
 fi
+if ! command -v logger >/dev/null 2>&1; then
+    printf "\n%sThis script requires 'logger' be installed to write entries to your journaling system. Exiting.%s\n\n" "$err" "$norm"
+    exit 2
+fi
 # turn off log file colourization if parameter is set
 if [ "$colourizeLogFile" -eq 0 ]; then
     bold=""