[Feature] Template card: allow for a numeric value in badge_icon

[Nickduino]

Requirements

• I have updated Mushroom to the latest available version
• I did a search to see if there is a similar issue or if a pull request is open.

Is your feature request related to a problem?

Nope

Describe the solution you'd like

I'd like to be able to display a numeric value (from templating) in a badge:

Describe alternatives you've considered

For numbers 0 to 10, there are material design icons available:

...but they are minuscule :-/

Additional context

I have two use cases in mind but there are probably many others:

• have an icon control a group of light, show the number of lights that are turned on (or the brightness value) in the badge
• have lightning detector: show the number of lightning recorded (or the distance of the last record) in the badge