pyproject. fix rut version.

fix replacing pytest and pyproject.toml

remove requirements files. everything on pyproject.toml

docs: fix analytics tracking.

tests: replace pytest with rut

site: tweak index, better sidebar nav.

doc: replace site index page with natice sphinx/furo.

use version as expected by doit.

start dev 0.38

ci: use pypy-3.11

remove dependency on doitpy.

bump version to 0.37

docs: rewrite README and site for clearer positioning

doc: fix #445, make it clear how task_dep works and suggest alternative.

docs: fix link to repology.