Remove as much javascript as possible

[icidasset]

Try to push more code into Elm and/or use one of the following:

• https://www.purescript.org/ (Use FFI?)
• https://derw-lang.github.io/ (compiles to Typescript, so we can use Web APIs?)
• https://gren-lang.org/ (not ready yet for our use-case, maybe effect modules in the future?)
• https://deno.land/ (just Typescript)
• https://gleam.run/ + https://github.com/bwireman/esgleam