Switched to shadow-cljs and deps.edn

[maxweber]

• Upgraded to the newest dependencies
• Removed om.next support (om.next is discontinued)
• Replaced marked with markdown Clojure lib
• Fixed highlight.js integration
• Made necessary changes to run the example devcards with shadow-cljs
• Adapted CSS integration

[maxweber]

I'm sorry, I wanted to merge this into the master of my repo