Follow the installation guide.
Though I followed it, I had a couple of errors.
Could not open library libsass.bundle no suitable image found
I had to reinstall it with --user-install option
gem uninstall sassc
gem install sassc --user-install
What is --user-install
When you use the --user-install option, RubyGems will install the gems to a directory inside your home directory, something like ~/.gem/ruby/1.9.1. The commands provided by the gems you installed will end up in ~/.gem/ruby/1.9.1/bin. For the programs installed there to be available for you, you need to add ~/.gem/ruby/1.9.1/bin to your PATH environment variable.
ruby 3 doesn't come with webrick any more.
jekyll cannot load such file -- webrick
So, install webrick additionally
bundle add webrick