[lit-starter-ts] fix missing mocha types

[majidsajadi]

Fixes #4594

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🦋 Changeset detected

Latest commit: ef2a2c8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@lit/lit-starter-ts	Patch

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[justinfagnani]

Thanks @majidsajadi

This is missing an update to the package-lock.json file. Run npm i to sync. We'll also need a changeset file, which you can generate with npm run changeset.