[Stepper] Allow customization of the icon text color

[mnogueron]

Description

It would be interesting to have the possibility to change the color of the text in the step lens as we can do with the icon color, directly from a muiTheme.

Images & references

Currently only these attributes are available to change the style of the lens.

stepper: {
      ...,
      iconColor: palette.primary1Color,
      hoveredIconColor: grey700,
      inactiveIconColor: grey500,
      ...
},

It would be interesting to add these:

stepper: {
      ...,
      iconColor: palette.primary1Color,
      hoveredIconColor: grey700,
      inactiveIconColor: grey500,
      iconTextColor: ... ,
      hoveredIconTextColor: ... ,
      inactiveIconTextColor: ... ,
      ...
},

So that we could be able to support better contrast between text and primary color.

(left: original, right: higher contrast with black text)

[Suresh-Lakum]

Can I have sample of how to use it?

I am right now using it when creating theme, but seems no effect.