Upgrade TypeScript to v4.9

[aaronccasanova]

WHAT is this pull request doing?

This PR upgrades the root TypeScript version to v4.9 and upgrades Polaris for Figma's ts-loader to address build failures.

TODO:

• Create snapshot release
• Tophat the Admin

How to 🎩

🖥 Local development instructions
🗒 General tophatting guidelines
📄 Changelog guidelines

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

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

export function Playground() {
  return (
    <Page title="Playground">
      {/* Add the code you want to test in here */}
    </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

[aaronccasanova]

Closing in favor of #7271