add help link to install zsh
add help link to install zsh

tekniklr/oh-my-zsh,nunogt/oh-my-zsh,tekniklr/oh-my-zsh,FrankSansC/oh-my-zsh,lightmanhk/oh-my-zsh,lightmanhk/oh-my-zsh,FrankSansC/oh-my-zsh,lightmanhk/oh-my-zsh,lightmanhk/oh-my-zsh,FrankSansC/oh-my-zsh,FrankSansC/oh-my-zsh,nunogt/oh-my-zsh