* [assets] Improve error message if no `index.html` could be found in the assets
* [assetoptions] Valide options that at least one property has been set
* [assetserver] Move defaultHTML handling for 404 from assethandler to assetserver
* [assetserver] Add support for serving the index.html file when requesting a directory
* [docs] Update changelog
* [assetserver] Add support for HTTP Middlewares
* [dev] Disable frontend DevServer if no Assets has been defined and inform user
* [dev] Consistent WebSocket behaviour in dev and prod mode for assets handler and middleware
In prod mode we can't support WebSockets so make sure the
assets handler and middleware never see WebSockets in dev mode.
* [templates] Migrate to new AssetServer option
* [docs] Add assetserver.Options to the reference
