Gauge card should allow attributes

[igorsantos07]

This is very simple, and AFAIK supported in many other places: allow an attribute property so we can use the original Gauge Card for stuff like Vacuum maintenance tasks (state of brushes/etc) and other things that don't get exposed as an entity on itself.

A template prop could be useful too, to help with custom information without having to resort to external things like Helpers and whatnot just to show on the dashboard.

Currently we have to go through HACS to get a clone-ish "custom gauge card" to get it to happen.