feat: add promise setup support

[roni-frantchi]

Adding the ability to export a function (potentially async) to resolve the configuration.
We found it particularly useful when resolving DynamoDB setup from the Serverless Framework, so one does not have to repeat ones own Dynamo table setup in code.
Could of course support other use cases as well.

module.exports = async () => {
  await serverless.init();
  const service = await serverless.variables.populateService();
  const tables = service.resources.Resources.filter(r => r.Type === 'AWS::DynamoDB::Table').map(
    r => r.Properties
  );

  return {
    tables,
    port: 8000
  };
};

[vladholubiev]

👍 Awesome! Thanks for the contribution!

[vladholubiev]

@roni-frantchi I've just published v1.2.0 🎉

[roni-frantchi]

Jest saw that - 🚀 Thanks @vladgolubev !