[DataTable] Allow JSX in the headers

[devonpmack]

WHY are these changes introduced?

Fixes #2597

We needed check boxes in our header but it was not supported. (Part of https://github.com/Shopify/store/issues/12522)

WHAT is this pull request doing?

Allow the header prop of DataTable to receive and display React Nodes.

How to 🎩

🖥 Local development instructions
🗒 General tophatting guidelines
📄 Changelog guidelines

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

import React from "react";
import { Card, DataTable, Page, Button } from "@shopify/polaris";

export default function DataTableExample() {
  return (
    <Page title="Sales by product">
      <Card>
        <DataTable
          columnContentTypes={[Array(5).fill("text")]}
          headings={Array(5).fill(<Button />)}
          rows={[]}
        />
      </Card>
    </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
• For visual design changes, pinged one of @ HYPD, @ mirualves, @ sarahill, or @ ry5n to update the Polaris UI kit

[github-actions]

💦 Potential splash zone of changes introduced to src/**/*.tsx in this pull request:

No significant changes to src/**/*.tsx were detected.

---

This comment automatically updates as changes are made to this pull request.
Feedback, troubleshooting: open an issue or reach out on Slack in #polaris-tooling.

[PabloVallejo]

🎩 Working correctly! and code looks 👌

maybe if we should write a test passing a react node to the headings!

[devonpmack]

@PabloVallejo Good call, I just added a test and example to component README.

[PabloVallejo]

Test and README ✅ 💯

[BPScott]

You can simplify the typing to just React.ReactNode[].

Petty but this appears in a few places so it's worth being as simple as possible :)

Fix up that and then this should be good to go

[devonpmack]

Thanks! I forgot that string was included. I've updated it to include your suggestion.

[dleroux]