fix(currency-input): Fix CurrencyInput not changing when empty value

[diogomateus]

What this PR does

This PR fixes the issue where CurrencyInput onChange was not triggering when the value was empty.
This PR also updates CurrencyInput to use storybook stories instead of mdx documentation.

How to test?

Remove the first if of the condition and observe that the empty value isn't triggering:

 if (shadowValue === '' && value) {
      onChange?.(null)
    } else if (shadowValue) {
      onChange?.(reverseFormatInput(shadowValue));
    }

Checklist:

• I reviewed my own code
• The changes align with the designs I received
  Or give a reason why this does not apply:
• I have attached screenshot(s), video(s) or gif(s) showing that the solution is working as expected
  Or give a reason why this does not apply:
• I have updated the task(s) status on Linear
• All new media is optimized (images, gifs, videos)

Browser support

My code works in the following browsers:

• Firefox
• Chrome
• Safari
• Edge

[diogomateus]

We should add more in-depth tests to this component in a following PR to be sure 👍