[Text field] Allow min and max to accept a string

[tmlayton]

WHY are these changes introduced?

Fixes #1988

WHAT is this pull request doing?

Allows number | string, updates the prop description

How to 🎩

🖥 Local development instructions
🗒 General tophatting guidelines
📄 Changelog guidelines

Copy-paste this code in playground/Playground.tsx:

import React, {useState} from 'react';
import {Page, TextField} from '../src';

export default function Playground() {
  const [value, setValue] = useState('2008-07-22');

  return (
    <Page title="Playground">
      <TextField
        label="Any time this decade 🙄"
        value={value}
        onChange={setValue}
        type="date"
        min="2010-01-01"
        max="2019-12-31"
      />
    </Page>
  );
}

🎩 checklist

• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility
• Updated the component's README.md with documentation changes
• Tophatted documentation changes in the style guide

[cboltt]

This will work for our use case! Cheers

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