Add default home assistant url to Wiki

[thomasaarholt]

Hi!

I see I can't edit the wiki directly. I'd like to suggest adding the following sentence to this wiki page.

"If you can access your home assistant in the web browser at homeassistant.local:8123, then the Host URL should be http://homeassistant.local:8123/ (note the http://)

The http:// is required for setting to work, homeassistant.local is not enough. Took me a few tries to work out what it wanted.