docs: use mkdocs for website docs

test/website-docs.spec.js

website/docs/assets/images/all-dead.jpg

website/docs/assets/images/broken-lockfile.jpg

website/docs/assets/images/github-app-choose-repos.png

website/docs/assets/images/github-app-install.png

website/docs/assets/images/logo.png

website/docs/assets/images/onboarding.png

website/docs/bazel.md

website/docs/config-presets.md

website/docs/configuration-options.md

website/docs/configuration-templates.md

website/docs/configure-renovate.md

website/docs/data-security.md

website/docs/dependency-pinning.md

website/docs/docker.md

website/docs/faq.md

website/docs/install-github-app.md

website/docs/javascript.md

website/docs/node.md

website/docs/noise-reduction.md