Documentation: Missing OBS repository installation instructions

[kansoit]

Description

I noticed that the README currently lacks instructions for installation via Linux distribution repositories. However, I discovered that the repository already exists on the OpenSUSE Build Service (OBS) under the zsh-users project, and I have verified that it works perfectly.

Discovery & Verification

While the documentation only mentions manual or plugin manager installs, the following repository is live and functional:
https://download.opensuse.org/repositories/shells:/zsh-users:/zsh-history-substring-search/

I have successfully tested the installation on Fedora using:

sudo dnf config-manager addrepo --from-repofile=[https://download.opensuse.org/repositories/shells:zsh-users:zsh-history-substring-search/Fedora_Rawhide/shells:zsh-users:zsh-history-substring-search.repo](https://download.opensuse.org/repositories/shells:zsh-users:zsh-history-substring-search/Fedora_Rawhide/shells:zsh-users:zsh-history-substring-search.repo)
sudo dnf install zsh-history-substring-search

Suggestion

Since zsh-users already maintains official OBS repositories for this and other plugins (like zsh-autosuggestions and zsh-syntax-highlighting), this information should be included in the README to help users who prefer system-managed packages.

Thanks!!