feat: add `onUnhandledError` callback

[sheremet-va]

Description

Closes #7675 Closes https://github.com/vitest-dev/vitest-browser-vue/issues/13

TODO

• [ ] Tests
• [ ] Docs

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• [ ] It's really useful if your PR references an issue where it is discussed ahead of time. If the feature is substantial or introduces breaking changes without a discussion, PR might be closed.
• [ ] Ideally, include a test that fails without this PR but passes with it.
• [ ] Please, don't make changes to pnpm-lock.yaml unless you introduce a new test example.

Tests

• [ ] Run the tests with pnpm test:ci.

Documentation

• [ ] If you introduce new functionality, document it. You can run documentation with pnpm run docs command.

Changesets

• [ ] Changes in changelog are generated from PR name. Please, make sure that it explains your changes in an understandable manner. Please, prefix changeset messages with feat:, fix:, perf:, docs:, or chore:.

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