Add audiences and format to transformer for query field.

[rcantin-w]

What does this change?

• Adds audiences and format to events query object in transformer, as an array of string (audiences labels) and single string (format label).
• Added them to the mapping
• Added them to the query, kind of copied from what was done in articles. I suggest going ahead with that and amending should we think a change is needed.

How to test

Run api locally and search for http://localhost:3000/events?query=chill-out, which is a format that previously returned no results.

How can we measure success?

Results are more useful and more fields return results.

Have we considered potential risks?

Updating the mapping will be required before running a reindex. I've never done it but have tested locally and adding fields to the mapping should be straightforward.