message: Add information about app-config.development.local.yaml to Development Environment page
diff: @@ -88,3 +88,14 @@ yarn create-plugin # Create a new plugin
  > See
  > [package.json](https://github.com/spotify/backstage/blob/master/package.json)
  > for other yarn commands/options.
  +
  +## Local configuration
  +
  +Backstage allows you to specify the configuration used while running the
  +application on your computer. Local configuration is read from
  +`app-config.development.local.yaml`. This file is ignored by Git, which means
  +that you can safely use it to reference secrets like GitHub tokens worrying
  +about these secrets inadvertently ending up in the Git repository.
  +
  +You can learn more about local configuration in
  +[Static Configuration in Backstage](../conf/) section.
  