Gerbil v0.18-rc1

Gerbil v0.18-rc1, the first release candidate for Gerbil v0.18 is ready!

• Release announcement: https://github.com/mighty-gerbils/gerbil/discussions/983
• Release tag and changelog: https://github.com/mighty-gerbils/gerbil/releases/tag/v0.18-rc1

Happy Hacking!