Updates to the @actual-budget/api package (#464)

* Make it easier to build the bundle.api.js for the API

* Remove budgetId parameter, move config to top level of API

* that’s a breaking change

* Add support for signing into the server in init()

* Add api.downloadBudget(syncId, { password }) method

* Fix lint errors

* Refactor: extract out getSyncError

* api/download-budget: sync if possible instead of downloading

* Don’t bother with fetching remote files and installing key if the file is local

* *groupId

* FIx lint issues

* Remove extra close+reopen

* Refactor out duplicate load-budget logic

* Trailing commas