J.E.S.S. is an alias for Jekyll Embedded Simple Server.
It's a lightweight Electron App which permit to run a Jekyll Server without installing Ruby, RubyGems and Jekyll.
npm install
bash download-binaries.sh
npm run start
The window will appear. Wait for the end of the installation.
Thanks to Louis-André Labadie who packaged Jekyll in a distributable version : L-A/Traveling-Jekyll.