Add go to root command on the external bus

[TimoPtr]

Currently on Android we have an option in the settings that allow the user to say that he always wants to open the default dashboard when he opens the app (including when he brings back the app from the background).
This option isn't working anymore since it was executing some JS code and was referencing paper-listbox which doesn't exist anymore.
In order to have a more reliable solution, we should have a dedicated command in the external bus for going to the default dashboard.

[TimoPtr]

home-assistant/android#5297 the initial issue.

[TimoPtr]

Implementation #25516