Updating most ebuilds often just requires copying and the file to a new version. There are a few commands run using the ebuild and pkgdev packages to do things like updating the package manifest.
More complex packages require an update to the build scripts, however this isn't typically the case between point releases.
See https://wiki.gentoo.org/wiki/Basic_guide_to_write_Gentoo_Ebuilds for a quick start guide.
You can submit PRs on GitHub (gentoo/gentoo); the community is welcoming and offers constructive feedback. And #gentoo-dev-help on IRC is available to provide support if you get stick.
Give it a try!
Edit:
It’s not really an issue for me, since I compiled the 0.9.18 version manually, but I’d like to know if there is anything I can do to help.
It's not a great idea to do that yourself. Learn to update ebuilds and have portage manage package updates for you; that why we have a package manager after all!