[Documentation] Updated list of supported Jest config overrides

[neilbryson]

There are now 14 Jest config keys that can be overriden through Create React App
https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/scripts/utils/createJestConfig.js#L72

This is just to update the list of available config overrides in the CRA site.

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[iansu]

Thanks!