jekyll local development instruments do not work

The instructions in the README on how to build locally do not work.

https://github.com/pytroll/pytroll.github.io/blob/f3aecd03041633b5d6b38e34e4577fbdf53cd760/README.md?plain=1#L23-L25

The step gem install fails with:

$ gem install rb-inotify jekyll
Fetching ffi-1.17.1-x86_64-linux-gnu.gem
Fetching rb-inotify-0.11.1.gem
ERROR:  Error installing rb-inotify:
        The last version of ffi (~> 1.0) to support your Ruby & RubyGems was 1.17.1. Try installing it with `gem install ffi -v 1.17.1` and then running the current command again
        ffi requires RubyGems version >= 3.3.22. The current RubyGems version is 3.1.4. Try 'gem update --system' to update RubyGems itself.
Fetching terminal-table-3.0.2.gem
Fetching safe_yaml-1.0.5.gem
Fetching forwardable-extended-2.6.0.gem
Fetching pathutil-0.16.2.gem
Fetching mercenary-0.4.0.gem
Fetching webrick-1.9.1.gem
Fetching unicode-display_width-2.6.0.gem
Fetching rouge-4.5.1.gem
Fetching liquid-4.0.4.gem
Fetching rexml-3.4.0.gem
Fetching kramdown-2.5.1.gem
Fetching kramdown-parser-gfm-1.1.0.gem
Fetching rb-fsevent-0.11.2.gem
Fetching listen-3.9.0.gem
Fetching jekyll-watch-2.2.1.gem
Fetching rake-13.2.1.gem
Fetching google-protobuf-4.29.3-x86_64-linux.gem
Fetching sass-embedded-1.83.1-x86_64-linux-gnu.gem
Fetching jekyll-sass-converter-3.0.0.gem
Fetching concurrent-ruby-1.3.4.gem
Fetching i18n-1.14.6.gem
Fetching http_parser.rb-0.8.0.gem
Fetching eventmachine-1.2.7.gem
Fetching em-websocket-0.5.3.gem
Fetching colorator-1.1.0.gem
Fetching public_suffix-6.0.1.gem
Fetching addressable-2.8.7.gem
Fetching jekyll-4.3.4.gem
Successfully installed webrick-1.9.1
Successfully installed unicode-display_width-2.6.0
Successfully installed terminal-table-3.0.2
Successfully installed safe_yaml-1.0.5
Successfully installed rouge-4.5.1
Successfully installed forwardable-extended-2.6.0
Successfully installed pathutil-0.16.2
Successfully installed mercenary-0.4.0
Successfully installed liquid-4.0.4
Successfully installed rexml-3.4.0
Successfully installed kramdown-2.5.1
Successfully installed kramdown-parser-gfm-1.1.0
ERROR:  Error installing jekyll:
        The last version of ffi (~> 1.0) to support your Ruby & RubyGems was 1.17.1. Try installing it with `gem install ffi -v 1.17.1` and then running the current command again
        ffi requires RubyGems version >= 3.3.22. The current RubyGems version is 3.1.4. Try 'gem update --system' to update RubyGems itself.

Running on openSUSE 15.3.

Start with README.md lines 23-25 and reproduce the documented local-build steps, especially gem install rb-inotify jekyll on the reported openSUSE 15.3 environment. Check the repository's Jekyll setup and update the instructions so the documented installation and local build work; verify the revised steps end-to-end.