Bump Fronter from f9a1fb2 to 18f6816 (#576)

Bumps [Fronter](https://github.com/ParadoxGameConverters/Fronter) from `f9a1fb2` to `18f6816`.
- [Commits](ParadoxGameConverters/Fronter@f9a1fb2...18f6816)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>