Add `setDataResidency` method to @sendgrid/mail default export

[kostia1st]

Please provide a simple wrapper function to @sendgrid/mail/src/classes/mail-service.js file with implementation along these lines:

  setDataResidency(region) {
    this.client.setDataResidency(region);
    
    return this;
  }

That would greatly simplify the approach to work with your new region feature for a lot of folks without the need to introduce any new dependencies into their projects.