Custom pipe

This is the completed Pipes project. It retains the previous site's pages, fragments, assets, and posts template. The page pipe now splits YAML front matter from Markdown and returns a slug as an alias.

From this directory:

cd project
falz build
falz watch --serve --hot-reload

Open /posts/first/ at the printed address. posts/hello.md produces dist/posts/first/index.html; the metadata is not rendered in the article. Root pages still use the built-in md pipe.

Continue with Index phase to make posts discover one another.