message: Clarify sidebars editing
diff: @@ -44,7 +44,7 @@ the code.
  where we keep all of our documentation Markdown files. These ends up on
  http://backstage.io/docs. Just keep in mind that changes to the
  [`sidebars.json`](https://github.com/spotify/backstage/blob/master/microsite/sidebars.json)
  - file also needs to be updated.
  + file may be needed as sections are added/removed.
  - [`.editorconfig`](https://github.com/spotify/backstage/tree/master/.editorconfig) -
  A configuration file used by most common code editors.
  