Serve playstore_api.json for Scriptoria

[FyreByrd]

sillsdev/appbuilder-portal#1258 (comment)

[chrisvire]

@FyreByrd See this comment:

We may have Build Engine do all the processing work. Scriptoria can communicate with multiple Build Engines, so Scriptoria may not have access to all of the secrets to do the work in the Scriptoria container.