Taken from here: https://discord.com/channels/608064116111966245/608064116984250379/1055555451569328179
Have 2 terminals running. In the first, start a web server:
ruby -run -e httpd ./builds/mygame-html5-0.1
in the second terminal, run the build:
./dragonruby-publish --only-package --platforms=html5 mygame
now navigate to localhost:8080