Documentation for how/why to use HttpServer

[bhudgeons]

This works great as a drop-in to provide Marshallers for Zio effects so that you can use them in routes. I also see that in the quickstart sample you're using HttpServer from this library. I have a feeling this is better than just dropping Zio effects into your "regular" Akka HTTP project. I'm trying to figure out why & how; I'll be happy to write up & share it when I can, but if there's an easy explanation, that would be great.

[vpavkin]

@bhudgeons Hi!
An easy explanation is that HttpServer is using ZLayer which fits nicely in a ZIO app. So if you're wiring your dependencies using ZLayer, our HttpServer would be a nice shortcut for you. Otherwise it's not that beneficial IMO.

I think it'll be a good addition to our readme, so a PR would be much appreciated 👍