For tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Lioli7k/tumbleweed/home:Lioli7k.repo
zypper refresh
zypper install zsh-autosuggestions
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Lioli7k/16.0/home:Lioli7k.repo
zypper refresh
zypper install zsh-autosuggestions
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Lioli7k/15.6/home:Lioli7k.repo
zypper refresh
zypper install zsh-autosuggestions