I have a Visual Studio 2017 solution with both an ASP.NET Web Application project (called UI) and an Azure WebJob project (called WebJobs). I have configured both to deploy
All you have to do is create the WebJob project by right clicking on your Web App and choosing:
Add / New Azure WebJob project
Or if you already have a WebJobs project in the solution:
Add / Existing WebJob project
Once you do that, publishing the Web App automatically publishes the WebJob where it belongs. It all happens in a single zip file, and there is nothing special to do in VSTS. Do not try to publish the WebJob project individually once you do that.