feat: add update lock file

Add functionality to create an update lock file when validating and updating SteamCMD. This prevents potential conflicts with customised files.

- Create a lock file with the current timestamp in the "command_validate.sh" script
- Create a lock file with the current timestamp in the "update_steamcmd.sh" script

lgsm/modules/command_validate.sh

@@ -23,7 +23,7 @@ fn_validate() {
 		fi
 	done
 	fn_print_warn_nl "Validate might overwrite some customised files"
-
+	date '+%s' > "${lockdir:?}/update.lock"
 	fn_dl_steamcmd
 }
 

lgsm/modules/update_steamcmd.sh

@@ -23,6 +23,7 @@ if [ "${forceupdate}" == "1" ]; then
 		exitbypass=1
 		command_stop.sh
 		fn_firstcommand_reset
+		date '+%s' > "${lockdir:?}/update.lock"
 		fn_dl_steamcmd
 		date +%s > "${lockdir}/last-updated.lock"
 		exitbypass=1