refactor(chapter1): tweak ui, add sections, set slideIndex in path

[KatvonRivia]

closes #1402

[andreashelms]

I think we need something like an anchor, that makes the scrolling stop at a certain point e.g. here:

But I don't know how this works with react-scroll-parallax.

[KatvonRivia]

I think we need something like an anchor, that makes the scrolling stop at a certain point e.g. here:

But I don't know how this works with `react-scroll-parallax`.

Yeah i tried using scroll-snap-type but it didnt work 🥲