[v3] Configure online editor

[ErikSchierboom]

This issue is part of the migration to v3. You can read full details about the various changes here.

In Exercism v3, students can now choose to work on exercises directly from their browser, instead of having to download exercises to their local machine. The track-specific settings for the in-browser editor are defined in the top-level "online_editor" field in the track's config.json file. This field is defined as an object with two fields:

• "indent_style": the indent style, either "space" or "tab".
• "indent_size": the indent size, which is an integer (e.g. 4).

You can find a full description of these fields in the spec.

Goal

The "online_editor" field should be updated to correspond to the track's best practices regarding indentation.

Example

"online_editor": {
  "indent_style": "space",
  "indent_size": 4
}

Tracking

exercism/v3-launch#2

[wolf99]

Seems the deafults are as above, they can probably be left as-is.
What do you think @ryanplusplus ?