Add `from` argument to `request_data()` and extensions

[mjwestgate]

It might be useful to enable users to specify a query from a non-default source without calling galah_config() first. This wouldn't change the defaults, only that one pipe. This could look like:

request_data(from = "Spain") |>
  count() |>
  collect()

I'd suggest the default value of from would be NULL and that it would default in that instance to the outcome of galah_config(), making this change fully backwards-compatible.

[daxkellie]

I like this idea. Would it similarly work in galah_call()?

[mjwestgate]

Yep, galah_call() and request_data() are synonymous, so would behave identically unless amended to act otherwise