chore: Upgrade jsdom to v21 which still supports Node 14

[Fullchee]

What:

• Upgrade jsdom to v21 which still supports Node 14

Why:

• fixes .toHaveStyle() doesn't know about aspect-ratio #570
• use the latest version of jsdom that supports Node 14

How:

Checklist:

• [ ] Documentation
• [ ] Tests
• [ ] Updated Type Definitions
• Ready to be merged
  

[Fullchee]

@fpapado @gnapse

Do we want to release a new major release of jest-dom@7which still supports Node 14?

We're upgrading jsdom@16 to jsdom@21

• => 5 breaking changes which might unwittingly break things in this library too

[Fullchee]

Resolves this issue

I copy pasted from this PR

https://github.com/testing-library/jest-dom/pull/568/files?w=1#diff-aac3f7b77b88910a3cab3e23a102333b446c87359e633f41c0441c7738791d5b

  ● Test suite failed to run

    ReferenceError: TextEncoder is not defined

      1 |
      2 |
    > 3 | import {JSDOM} from 'jsdom'
        | ^
      4 | import {render} from './helpers/test-utils'
      5 |
      6 | /*