🤖 Add Ace editor and highlightjs languages to config.json

[ErikSchierboom]

This PR adds adds two new keys to the online_editor property in the config.json files:

1. ace_editor_language: the language identifier for the Ace editor that is used to edit code on the website
2. highlightjs_language: the language identifier for Highlight.js which is used to highlight code on the website

For more information, see https://github.com/exercism/docs/pull/124/files

Maintainer TODO list

We've pre-populated the values for the two new keys with the track's slug, which is probably the correct value for most tracks. Please check these values are correct for your track:

• [ ] The ace_editor_language value is correct. See the full list of identifiers (filenames, not directories).
• [ ] The highlightjs_language value is correct. See the full list of identifiers

Tracking

https://github.com/exercism/v3-launch/issues/32