Feature request: Add include file to web_handler

[MikeOne70]

Hi,

Could be possible to add html file on web_handler in funcion stream.print() or a new one like stream.file or stream.include("mywebpage.html")?

It should be a nice addon for made sensor graphical board with gauges on esphome.

Also should be interesting if esphome webserver main page can be linked on another folder like http://xxx.xxx.xxx.xxx/advance and custom html on root / url

Thanks in advance

Mike