Add option to download search results in parquet format

[afg1]

Adds an option to download in parquet format from text search results. Relies on the changes in the export microservice from RNAcentral/rnacentral-export#1

Given that parquet is a tabular format and should be able to handle the same data types as json, I don't think it needs a genes filter, but that will have to be tested more thoroughly

[Isaac1m]

Looks good @afg1! Are we generating the parquet files on the fly, or retrieving them from some db/object storage?

[afg1]

Thanks! Yeah, the parquet is generated on the fly by the export microservice in the other PR, it's mostly reusing the way that the JSON download is generated. We will need to deploy that before this can go live on the site, we're just figuring out the least risky way to do that without breaking prod

[Isaac1m]

Sounds good, we can deploy it to test once it’s ready before moving to prod. Happy to merge this change!