chore(deps): [security] bump acorn from 6.2.0 to 6.4.1 (#21)

Bumps [acorn](https://github.com/acornjs/acorn) from 6.2.0 to 6.4.1. **This update includes security fixes.**
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.2.0...6.4.1)

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Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>