Provide test/example for promise_batch_action_* calls

[mikedotexe]

Use case
As I user, I want to use the methods listed around here:

near-sdk-as/assembly/runtime/env/imports.ts

Line 129 in a7dcaf3

@external("env", "promise_batch_action_transfer")

in order to make batch promise calls. I would like to take an example from either a test (probably simulation test in this case) that uses batch promises, or have some examples in comments to model after.

Acceptance Criteria
Code is available in near-sdk-as in a way that a user can copy/paste and modify batch promise calls in order to use in their own smart contract.

[willemneal]

fixed by #86