[Feature]: DateField improvements

[nuno-am]

Describe the feature

ℹ️ I've recently started looking into the DateField component, but from my brief investigation, I couldn't find answers for what I'll consider now as feature requests for it.

• Format filled segments with leading zeros

  • Whether via a new prop or a formatting function, I'd like to have a possibility of displaying a leading 0 for date segments, namely for day and month;
  • I see now that this automatically happens depending on the current locale...

• Possibility to tell if a segment has a value or not

  • I believe this is possible right now, by checking if the value for a given segment is actually a number, but a built-in mechanism would be preferable
  • This is useful to style the segment accordingly. For example:
    • No value: color it like a placeholder (like a shade of gray)
    • Has value: color it like a regular input value (like black)
  • I was able to customize it via data-[placeholder] class

• Possibility of having a property (data-attribute, for example) on the Root component, that informs if one of the segments currently has a focus.

  • This is useful to display an outline on the root input, similar to what a regular text input would have, if it was focused.
  • I managed to solve it by placing @focus/@blur events on the DateFieldInput components that update a ref. Then I used a data-focused attribute on the DateFieldRoot based on that ref value. Not sure if that's the right approach, though...

Apologies if any of these features already exist. I simply wasn't able to figure them out.

Additional information

• I intend to submit a PR for this feature.
• I have already implemented and/or tested this feature.