Added scheduler warning

languages/en.yaml

@@ -786,6 +786,7 @@ PLUGIN_ADMIN:
   SCHEDULER_OUTPUT_TYPE_HELP: "Either append to the same file each run, or overwrite the file with each run"
   SCHEDULER_EMAIL: "Email"
   SCHEDULER_EMAIL_HELP: "Email to send output to. NOTE: requires output file to be set"
+  SCHEDULER_WARNING: "The scheduler uses your system's crontab system to execute commands. You should use this only if you are an advanced user and know what you are doing. Misconfiguration or abuse can lead to security vulnerabilities."
   SECURITY: "Security"
   XSS_SECURITY: "XSS Security for Content"
   XSS_WHITELIST_PERMISSIONS: "Whitelist Permissions"

themes/grav/templates/partials/tools-scheduler.html.twig

@@ -14,6 +14,8 @@
         <div class="alert warning"> {{ "PLUGIN_ADMIN.SCHEDULER_NOT_ENABLED"|tu }}</div>
     {% endif %}
 
+    <div class="alert notice"><i class="fa fa-exclamation-circle"></i> {{ "PLUGIN_ADMIN.SCHEDULER_WARNING"|tu([user]) }}</div>
+
     <div id="cron-install" class="form-border overlay {{ cron_status == 1 ? 'hide' : ''}}">
         <pre><code>{{- grav.scheduler.getCronCommand()|trim -}}</code></pre>