For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jsulig:branches:devel:languages:ruby:extensions/openSUSE_Tumbleweed/home:jsulig:branches:devel:languages:ruby:extensions.repo
zypper refresh
zypper install rubygem-kramdown-parser-gfm
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jsulig:branches:devel:languages:ruby:extensions/16.0/home:jsulig:branches:devel:languages:ruby:extensions.repo
zypper refresh
zypper install rubygem-kramdown-parser-gfm
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:jsulig:branches:devel:languages:ruby:extensions/15.6/home:jsulig:branches:devel:languages:ruby:extensions.repo
zypper refresh
zypper install rubygem-kramdown-parser-gfm