create full @magic page from readme.md

[jaeh]

now that @magic supports markdown,
we can simply create a page and menu from the readme of any repository.

to achieve:

1. add config switch ("readme: true")
2. instead of searching for files in dir tree, just load readme.md.
3. get all h2 and h3 and generate a deeply nested menu out of their ids and text.
4. create a index page from the readme contents

done.

bonus:

• add gitbadges if user has them in readme
• try to find logo image from readme
• try to find a menu near the top of the page for custom menu
• the --- @State { --- comment at the top of the page exports the state, allows all settings that normally get done in app.mjs