fix: Fix FileInput in SSR

[sawyerh]

Summary

navigator is only available in a browser environment, and calling it on the server causes an exception.

Checking if navigator is defined isn't enough however, since that causes a different React error:

Error: Text content does not match server-rendered HTML.

See more info here: https://nextjs.org/docs/messages/react-hydration-error

To resolve both issues, I've followed the suggestion in the link above, to run the check in useEffect.

Related Issues or PRs

Resolves #2366

How To Test

I tested this locally with a Next.js app by:

1. Running yarn build
2. Running npm link in the library's directory
3. Running npm link @trussworks/react-uswds in the Next.js project
4. Rendering FileInput in the Next.js project
5. Running npm run dev in the Next.js project and confirming no errors occur

Screenshots

[brandonlenz]

Hey @sawyerh long time no see 😉! Just one small thing before I approve. Changes are working well for me

[brandonlenz]

@all-contributors add @sawyerh for code

[allcontributors]

@brandonlenz

I've put up a pull request to add @sawyerh! 🎉