build(deps): bump minimatch, recursive-readdir and serve-handler

Bumps [minimatch](https://github.com/isaacs/minimatch), [recursive-readdir](https://github.com/jergason/recursive-readdir) and [serve-handler](https://github.com/zeit/serve-handler). These dependencies needed to be updated together.

Updates `minimatch` from 3.0.4 to 3.1.2
- [Release notes](https://github.com/isaacs/minimatch/releases)
- [Commits](isaacs/minimatch@v3.0.4...v3.1.2)

Updates `recursive-readdir` from 2.2.2 to 2.2.3
- [Release notes](https://github.com/jergason/recursive-readdir/releases)
- [Changelog](https://github.com/jergason/recursive-readdir/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jergason/recursive-readdir/commits/v2.2.3)

Updates `serve-handler` from 6.1.3 to 6.1.5
- [Release notes](https://github.com/zeit/serve-handler/releases)
- [Commits](vercel/serve-handler@6.1.3...6.1.5)

---
updated-dependencies:
- dependency-name: minimatch
  dependency-type: indirect
- dependency-name: recursive-readdir
  dependency-type: indirect
- dependency-name: serve-handler
  dependency-type: indirect
...

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