Website rework, moving on from mkdocs

[Tremeschin]

The current "version" of the website using mkdocs won't get any more updates or deployments, for a couple reasons:

I'm having a great experience using zensical - mkdocs-material' spiritual successor. While the monorepo and shared project structure worked for a while, it has got too spaghetti and unstable to work with this much customization and automation. It's something zensical will naturally evolve into their roadmap, and I'm having joy for once writting self-contained documentation for https://pyaket.dev/. Much less dependencies too!

While at it, it's best to:

• Improve installation instructions, recommend a fixed python version in uvx
• Fix the parameters documentation videos unavailable (a friend stopped its vps)
• Add a clear Community, Credits, License, etc. tabs in the homepage
• Figure out distribution of Pyaket executables for sustainability

For an ETA on when things will happen, see the meta issue below!