Middleware to handle requests by passing them through to an instance of the Vue CLI server. This means you can always serve up-to-date CLI-built resources without having to run the Vue CLI server manually.
Shamelessly based on https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.spaservices.angularcli.angularclimiddlewareextensions.useangularcliserver?view=aspnetcore-2.2 with small changes to enable it to work with Vue.