'Finalize' markdown file format

Triggered by #36 (closed), let's discuss the format we have, and whether it can be called final or not.

Personally, I think that before moving to a world where bulk editing is impossible, we should make sure to have covered everything that's necessary for good app listings.

Let's start by large and go down to smaller issues:

• going fully TOML: originally, I wanted to realize the site in pure TOML. The reason for having descriptions and notice as Markdown outside TOML was search (BTW: we could still have some markdown inside TOML). If we take another approach that's implemented in the abridge theme that allows for alternate search implementations, the original reasoning is no longer valid.
  • won't do
• ratings: There are valid concerns about the ratings. I've been pondering this for a long time, and IMHO to really improve things, it's necessary to split things out: mobile fit (does the app fit a typical linux phone screen), "touchability" (we need a better term, but this is how well things work with touch input only **), and maybe another thing I have not yet considered.
• alternate flatpak stores, flatpak recipes, and flathub:
• snaps ;-)
• a world taxonomy (Plasma Mobile, GNOME on Mobile as examples) - won't do.
• what about tablets? - to complicated to tackle now.
• more, you tell me 😄

** E.g.: Seahorse, GNOME's password store. It fits just fine, but some features are just hidden and right-mouse-click only.