Is there a DragonRuby website that contains docs, tutorials, etc. ?

I don't believe a website exists yet beyond the itch pages.  https://wndx.school/p/dragon-ruby-game-toolkit-tutorial is a good video tutorial introduction and I recommend joining the #gamedev Slack channel https://slack.rubymotion.com/

Awesome DragonRuby

https://github.com/awesome-dragonruby/awesome-dragonruby