Rewrite to Kotlin-js

[Zomis]

This project would benefit from being rewritten to Kotlin and having the client in Vue or some other JavaScript framework, possibly using "pure" Kotlin-js.

Benefits would be:

• No groovy, more modern technology
• Faster (Groovy has lots of black slow magic behind the screens)
• Easier to access and deploy
• Kotlin! (Cleaner code and just a lot nicer to work with)

[Zomis]

For background tasks (Kotlin coroutines) try https://www.npmjs.com/package/vue-worker