Get rid of VueJS

[kirushik]

Well, there's nothing in BananaSplit which requires reactivity and advanced templating.
VueJS worked really well during the prototyping phase, but now when the project is more mature, it both increases the resulting html size, introduces a lot of dependencies to trust, and complicates the build.

Bonus points for moving to a build system which would be supported by LavaMoat to make #36 possible.

[kirushik]

This will also allow for configs to be brought closer to the ones of our other relevant JS projects, for example with https://github.com/polkadot-js/dev/blob/master/packages/dev/config/jest.js