Make render async

[dbartholomae]

At the moment, the full rendering process is synchronous. This prevents us from writing components that fetch data asynchronously, e. g. via a web request. Since markdown is only used for one-off rendering without any interactivity, we don't have to worry about loading states. Therefore we can find a simple solution for asynchronous rendering.

Describe the solution you'd like

Make render asynchronous, so that it renders the existing components as before.

Describe alternatives you've considered

React uses hooks and state to manage asynchronous rendering. This seems to be too complicated for this usecase, though.

Additional context

This is preparation for #2

[KwanJunWen]

Hi, I am interested on this issue, can I try this ?

[dbartholomae]

Hi! I've already started on this since no one seemed to have noticed the repo, but if you are interested I could wrap up my refactors next week and then next weekend you could take over :)