Bump cppfront from 4a24618 to a18d22e

Bumps [cppfront](https://github.com/hsutter/cppfront) from `4a24618` to `a18d22e`.
- [Release notes](https://github.com/hsutter/cppfront/releases)
- [Commits](hsutter/cppfront@4a24618...a18d22e)

---
updated-dependencies:
- dependency-name: cppfront
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>