Update vfile to 4.2.1

[yukukotani]

Subject of the feature

I'd like you to release a new version of unified with vfile 4.2.1

Problem

vfile 4.2.1 includes this PR. With this change, users are able to use unified (and remark) in browser without path polyfill.

This change is a big improvement but the latest unified (9.2.0) still includes vfile 4.2.0.

Also, many repositories in unified ecosystem ignore package-lock.json and yarn.lock by .gitignore. Without them, the version of dependencies determined by the timing of npm install, so we cannot reproduce the behavior of a specific version. Maybe you should include them in the repository.

Expected behavior

The new version of unified and remark with latest dependencies are released.

Alternatives

[wooorm]

You can npm update or remove your yarn lock and reinstall to get the update.

Adding package locks / yarn locks here has no effect on how you consume this project.