chore: add unplugin-vue-router to readme

[hannoeru]

Description

Redirect Vue user to unplugin-vue-router.

Additional context

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What is the purpose of this pull request?

• [ ] Bug fix
• [ ] New Feature
• [x] Documentation update
• [ ] Other

Before submitting the PR, please make sure you do the following

• [x] Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• [x] Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• [ ] Ideally, include relevant tests that fail without this PR but pass with it.