Docs: add dashboards folder naming guidance (#74772)

* Added folder naming guidance

* Fixed prettier linting errors

docs/sources/dashboards/manage-dashboards/index.md

@@ -58,6 +58,8 @@ Folders help you organize and group dashboards, which is useful when you have ma
 1. On the Dashboards page, click **New** and select **New folder** in the dropdown.
 1. Enter a unique name and click **Create**.
 
+   Do not use the name of a folder that has already been provisioned (such as "General") and avoid special characters (except underscores and hyphens).
+
 When you save a dashboard, you can either select a folder for the dashboard to be saved in or create a new folder.
 
 ## Manage dashboards