Open dashboard by default

[bo0tzz]

Is your feature request related to a problem? Please describe.
When I open z2m, I'm almost always looking for the dashboard to turn on a device or look at some readouts.

Describe the solution you'd like
A setting to open the dashboard by default when navigating to the root path.

Describe alternatives you've considered
Adding a bookmark link that takes me directly to the dashboard.

Additional context
If someone can tell me where a setting for this would best live, I'd be happy to try my hand at a PR.