feat(react): update to support react 17

[scurker]

closes #1473

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[anastasialanz]

Also closes https://github.com/dequelabs/cauldron/issues/1473

[scurker]

Also closes #1473

AHHHHHHH auto completion got me and I didn't check the ticket that this one was supposed to close 😅

[anastasialanz]

Closing this for https://github.com/dequelabs/cauldron/pull/1680 since I'm taking over the work and then @scurker can be a reviewer of the PR too.