request_make() should probably default to `encode = "json"`

[jennybc]

Does this work with all httr verbs?

As I work on googlesheets4 and reflecting on googledrive, I think we (almost?) always want encode = "json", so that would be a much better default.

[JosiahParry]

Giving this a thumbs up. Was bamboozled by this. I was running into Unsupported content with type: multipart/form-data; boundary when trying to create nested param lists. The answer was encode = "json".

Reference: https://github.com/JosiahParry/gcalendr/blob/78cb7c404a84c0bd9d53c2314e8e7b51589b4ff0/R/create_event.R#L27