rubygem-rails-html-sanitizer from SUSE:SLE-15:Update project

需要 pool ，用 root 執行：

zypper addrepo https://download.opensuse.org/repositories/SUSE:SLE-15:Update/pool/SUSE:SLE-15:Update.repo
zypper refresh
zypper install rubygem-rails-html-sanitizer