Update toolchain and cleanup code

This MR updates the build toolchain to Vue CLI 5 and Tailwind 3.x, cleanes up some code, and removes some unused libraries.

Upgrading the toolchain wasn’t really my intention at first, but the linter complained about a lot of code when I started the dev server. Auto-formatting the code caused some very weird issues though, like completely unindented HTML in some places. Instead of trying to find a fix for these issues with the old tooling I figured that we’d be better off with the using the updated tooling and fix things from there. Fortunately most problems were fixed by the migration.

I’ve noticed that there are still quite a few issues after applying the linting configuration, so I’ve opened #95 (closed).