message: docs: added note about marking frontend config visible
diff: @@ -132,5 +132,10 @@ copy everything from the default config to the local config.
  `app-config.local.yaml` will be merged with `app-config.yaml` and overwrite the
  default app configs.
  +> NOTE: If you want to add your own configuration values to access in the
  +> frontend you also need to mark those values as visible using configuration
  +> schema, either in the app or in your own plugin. For more information, see
  +> [Defining Configuration](../conf/defining.md)
  +
  You can learn more about the local configuration in
  [Static Configuration in Backstage](../conf/) section.
  