Bump acorn from 6.1.1 to 6.4.2
Bump acorn from 6.1.1 to 6.4.2

Bumps [acorn](https://github.com/acornjs/acorn) from 6.1.1 to 6.4.2.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](https://github.com/acornjs/acorn/compare/6.1.1...6.4.2)

---
updated-dependencies:
- dependency-name: acorn
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
jviotti/unicode-length