Pin Typescript to >=v4.2

[vanessayuenn]

Currently, our package.json suggests we support all versions of typescript:

storybook/code/renderers/react/package.json

Line 87 in 5b34161

"typescript": "*"

^ That is not entirely true since we have a dependency on type-fest@2 that supports typescript >=4.2 only.

That said, in order to keep up with the ecosystem and set expectations with users, we should be more explicit and specific with which typescript version we support. Since this will be a breaking change, 8.0 will be an opportunity for us to make this change.

Context: this came up when we discussed how to resolve #23554