README: and another hint on RouterOS version

... for individual scripts. Just add it in comment with
"certificate=...". This also works on installtion:

$ScriptInstallUpdate new-script "base-url=..., certificate=...";

Closes: https://github.com/eworm-de/routeros-scripts/pull/97

README.md

@@ -122,6 +122,9 @@ And finally load configuration and functions and add the scheduler.
 
 ![screenshot: run and schedule scripts](README.d/05-run-and-schedule-scripts.avif)
 
+> 💡️ **Hint**: You see complaints regarding syntax errors? Most likely the
+> RouterOS on your device is too old. Check for updates!
+
 ### Scheduled automatic updates
 
 The last step is optional: Add this scheduler **only** if you want the

global-functions.rsc

@@ -1195,6 +1195,12 @@
         :error true;
       }
 
+      :if ([ :len ($ScriptInfo->"certificate") ] > 0) do={
+        :if ([ $CertificateAvailable ($ScriptInfo->"certificate") ] = false) do={
+          $LogPrint warning $0 ("Downloading certificate failed, trying without.");
+        }
+      }
+
       :do {
         :local BaseUrl [ $EitherOr ($ScriptInfo->"base-url") $ScriptUpdatesBaseUrl ];
         :local UrlSuffix [ $EitherOr ($ScriptInfo->"url-suffix") $ScriptUpdatesUrlSuffix ];