Use pre-commit to lint source code

We can now use pre-commit to run linters on the frontend:

• eslint with previously used plugin (vue support)
• basic pre-commit sanity checks
• codespell

The only downside is that I had to remove eslint-loader from runtime: i guess there are no more warnings while working (but they are auto fixed through pre-commit)

I managed to keep eslint-loader at runtime: eslint and deps are still managed (and upgraded 🎉 by npm), but usable by pre-commit