Add binding for application:get_application()

[ctrlaltmilk]

This adds a binding to get_application/0 from the Erlang application module, for use mainly with application.priv_directory(). For example, a web server could expose a function to automatically serve static files from the current application's priv directory.

I briefly considered binding to get_application/1, but that would require either separate functions for getting the application from a PID/module name or a new type, and it's much less common to have multiple applications running in Gleam than in Elixir or Erlang.

[lpil]

Hello! How did you verify this to be working? There's no tests!

[ctrlaltmilk]

I tested it separately - from what I can see, the tests don't run inside an application so the only test would be

let assert Error(_) = application.get_application()

If you want it, I can add it - not sure if there's any way to spin up an application inside a test so that the success case gets checked.