Rework tutorials

[oliversturm]

Similar to templates and demos, tutorials should be more focused than they are now - perhaps they were focused in the past, but now reSolve supports various strategies, like using HOCs vs Hooks, etc.

We want tutorials to be straight-forward to follow, and I suggest they should be opinionated to achieve this. We can link to other content about alternative approaches, but we need a stringent approach to describe the "currently recommended" way of doing things in the main tutorials.