Build: Change rootDir in TS plugin

[tmeasday]

Issue: TS not working for our own project

What I did

Correct the root path passed to the plugin. Although viteConfig.root is incorrect, the vite build appears to use the correct paths so I didn't actually change the value passed to vite (should I?)

How to test

Make a small change in a PR-- see

• Change rootDir in TS plugin #20912
• https://www.chromatic.com/build?appId=635781f3500dd2c49e189caf&number=2627

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[IanVS]

This works for me. If Vite's building happily then I think this is the correct change.

[ethriel3695]

@tmeasday You got it!

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